Forums

Zenering a big transistor

Started by George Herold June 26, 2017
On Tuesday, June 27, 2017 at 12:51:20 PM UTC-4, John Larkin wrote:
> On Tue, 27 Jun 2017 09:12:14 -0700 (PDT), George Herold > <gherold@teachspin.com> wrote: > > >On Tuesday, June 27, 2017 at 10:02:22 AM UTC-4, John Larkin wrote: > >> On Mon, 26 Jun 2017 18:02:21 -0700 (PDT), dagmargoodboat@yahoo.com > >> wrote: > >> > >> >On Monday, June 26, 2017 at 8:17:45 PM UTC-4, dagmarg...@yahoo.com wrote: > >> >> On Monday, June 26, 2017 at 5:33:47 PM UTC-4, John Larkin wrote: > >> >> > On Mon, 26 Jun 2017 14:21:43 -0700 (PDT), dagmargoodboat@yahoo.com > >> >> > wrote: > >> >> > > >> >> > >On Monday, June 26, 2017 at 1:15:44 PM UTC-4, John Larkin wrote: > >> >> > >> On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), dagmargoodboat@yahoo.com > >> >> > >> wrote: > >> >> > >> > >> >> > >> >On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: > >> >> > >> >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: > >> >> > >> >> > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) > >> >> > >> >> > There's a couple of depletion fets in series as current limiters. (LND150) > >> >> > >> >> > The b-e junction starts to zener at ~30 V (only two tested so far). > >> >> > >> >> > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? > >> >> > >> >> > Will it take time? I'm going to measure forward voltage again after > >> >> > >> >> > zenering for 15 minutes. Should I measure something else too? > >> >> > >> >> > > >> >> > >> >> > TIA > >> >> > >> >> > > >> >> > >> >> > George H. > >> >> > >> >> > >> >> > >> >> Why not just protect your TIP31C from zenering? A few diodes would do it. > >> >> > >> >> > >> >> > >> > > >> >> > >> >e.g., > >> >> > >> > | > >> >> > >> > +----. > >> >> > >> > | | > >> >> > >> >TIP31C |<' --- > >> >> > >> > .---| ^ D1 > >> >> > >> > | |\ | > >> >> > >> > | | | > >> >> > >> > '-----+----' > >> >> > >> > | > >> >> > >> > | > >> >> > >> > > >> >> > >> >Add a zener in series with D1 if you need to stand off some reverse voltage. > >> >> > >> > > >> >> > >> >Cheers, > >> >> > >> >James Arthur > >> >> > >> > >> >> > >> Or use the c-b junction instead. > >> >> > > > >> >> > >That loses the transistor action, degrading its temperature-sensing > >> >> > >performance. > >> >> > > > >> >> > >Cheers, > >> >> > >James Arthur > >> >> > > >> >> > Think so? It's still a diode with a roughly -2 mV/K tempco. > >> >> > >> >> I read that ages ago, in an early article about using Motorola transistors > >> >> specifically spec'd as temperature sensors IIRC. (It's amazing I can > >> >> remember that. Still have the article somewhere, I'm sure.) > >> >> > >> >> > No transistor will ever be a super-accurate temp sensor. > >> >> > >> >> Delta Vbe is good pretty easily to +/-1oC, uncalibrated. > >> >> > >> >> > There is an LM35 available in TO220. > >> >> > > >> >> > Zetex makes a cool 1K ohm SOT23 nickel RTD too. Nickel is cool because > >> >> > the curve slopes up, so you can linearize it by just loading it. RTDs > >> >> > are tough and don't rectify RF or oscillate. > >> >> > >> >> Can't argue with RTDs... > >> >> > >> >This has interesting measurements of a variety of vendors' 2n3904's: > >> > > >> >http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf > >> > > >> > "Figure 2 also shows why true 2-terminal discrete diodes > >> > are not used in temperature sensing applications instead > >> > of 3-terminal devices such as the 2N3904. > >> > > >> > A discrete 2-terminal diode, ideally, would perform in > >> > temperature sensing applications as well as a thermal > >> > diode would. However, characterization in the labs > >> > determined that discrete 2-terminal diodes typically > >> > have an ideality factor much higher (1.2&ndash;1.5) than > >> > ? ASSUMED of 1.004. This discrepancy (between ? ASSUMED > >> > and ? REAL) would cause unacceptable temperature > >> > measurement errors at all temperatures." > >> > >> "Unacceptable" is arbitrary and judgemental. It's kinda prissy, going > >> around assuming stuff. > >> > >> > > >> >I just read a number delta Vbe app notes; all recommend diode-connected > >> >transistors over diodes. > >> > > >> >Cheers, > >> >James Arthur > >> > >> I don't care about ideality factor, how well a c-b junction might > >> match some theoretical ideal-diode equation. What matters is how well > >> you calibrate the V-T curve of a device, and how similar later devices > >> might be. > > > >I sorta agree, If I could find a diode that was repeatable and easily > >calibrated against some standard that would be fine. > > Buy the transistors from the same vendor, no matter how you process > the signals. Ideally, but a reel that's a lifetime supply. > > Seems to me that you can't avoid some actual temperature measurements, > unless you buy an IC or an RTD that has guaranteed specs. > > > > > >The one nice thing about the 'ideal' behavior is that you can check the > >calibration (very roughly) by looking at the signal as a function of bias > >current. That nice.. and also nice physics. > > > >George h. > > In your production units, are you planning to do the theoretical > delta-I/deltaV math, or are you just going to use a constant current > and measure the diode voltage drop?
For production, I measure a temperature* and a voltage drop at CC. And then generate a table of V vs T. I tell them about the delta I/ delta V thing.. I'm guessing most everyone just ignores it, it's only EE geek types that like that kind of thing.
> > How accurate do you need it to be?
Right, one degree (C or K) is plenty good for most things. Resolution, and changes in temperature are more important. George H. *I've got a calibrated diode from lakeshore, which is my temperature 'standard'. I tack that onto the transistor.
> > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
On Tuesday, June 27, 2017 at 1:03:33 PM UTC-4, dagmarg...@yahoo.com wrote:
> On Tuesday, June 27, 2017 at 10:02:22 AM UTC-4, John Larkin wrote: > > On Mon, 26 Jun 2017 18:02:21 -0700 (PDT), dagmargoodboat@yahoo.com > > wrote: > > > > >On Monday, June 26, 2017 at 8:17:45 PM UTC-4, dagmarg...@yahoo.com wrote: > > >> On Monday, June 26, 2017 at 5:33:47 PM UTC-4, John Larkin wrote: > > >> > On Mon, 26 Jun 2017 14:21:43 -0700 (PDT), dagmargoodboat@yahoo.com > > >> > wrote: > > >> > > > >> > >On Monday, June 26, 2017 at 1:15:44 PM UTC-4, John Larkin wrote: > > >> > >> On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), dagmargoodboat@yahoo.com > > >> > >> wrote: > > >> > >> > > >> > >> >On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: > > >> > >> >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: > > >> > >> >> > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) > > >> > >> >> > There's a couple of depletion fets in series as current limiters. (LND150) > > >> > >> >> > The b-e junction starts to zener at ~30 V (only two tested so far). > > >> > >> >> > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? > > >> > >> >> > Will it take time? I'm going to measure forward voltage again after > > >> > >> >> > zenering for 15 minutes. Should I measure something else too? > > >> > >> >> > > > >> > >> >> > TIA > > >> > >> >> > > > >> > >> >> > George H. > > >> > >> >> > > >> > >> >> Why not just protect your TIP31C from zenering? A few diodes would do it. > > >> > >> >> > > >> > >> > > > >> > >> >e.g., > > >> > >> > | > > >> > >> > +----. > > >> > >> > | | > > >> > >> >TIP31C |<' --- > > >> > >> > .---| ^ D1 > > >> > >> > | |\ | > > >> > >> > | | | > > >> > >> > '-----+----' > > >> > >> > | > > >> > >> > | > > >> > >> > > > >> > >> >Add a zener in series with D1 if you need to stand off some reverse voltage. > > >> > >> > > > >> > >> >Cheers, > > >> > >> >James Arthur > > >> > >> > > >> > >> Or use the c-b junction instead. > > >> > > > > >> > >That loses the transistor action, degrading its temperature-sensing > > >> > >performance. > > >> > > > > >> > >Cheers, > > >> > >James Arthur > > >> > > > >> > Think so? It's still a diode with a roughly -2 mV/K tempco. > > >> > > >> I read that ages ago, in an early article about using Motorola transistors > > >> specifically spec'd as temperature sensors IIRC. (It's amazing I can > > >> remember that. Still have the article somewhere, I'm sure.) > > >> > > >> > No transistor will ever be a super-accurate temp sensor. > > >> > > >> Delta Vbe is good pretty easily to +/-1oC, uncalibrated. > > >> > > >> > There is an LM35 available in TO220. > > >> > > > >> > Zetex makes a cool 1K ohm SOT23 nickel RTD too. Nickel is cool because > > >> > the curve slopes up, so you can linearize it by just loading it. RTDs > > >> > are tough and don't rectify RF or oscillate. > > >> > > >> Can't argue with RTDs... > > >> > > >This has interesting measurements of a variety of vendors' 2n3904's: > > > > > >http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf > > > > > > "Figure 2 also shows why true 2-terminal discrete diodes > > > are not used in temperature sensing applications instead > > > of 3-terminal devices such as the 2N3904. > > > > > > A discrete 2-terminal diode, ideally, would perform in > > > temperature sensing applications as well as a thermal > > > diode would. However, characterization in the labs > > > determined that discrete 2-terminal diodes typically > > > have an ideality factor much higher (1.2&ndash;1.5) than > > > ? ASSUMED of 1.004. This discrepancy (between ? ASSUMED > > > and ? REAL) would cause unacceptable temperature > > > measurement errors at all temperatures." > > > > "Unacceptable" is arbitrary and judgemental. It's kinda prissy, going > > around assuming stuff. > > If we stop being offended and look at the figures, though, discrete diodes > had large and unpredictable variations, while transistors' variations were > small and consistent. That's what I got from the same paragraph, anyhow. > > > >I just read a number delta Vbe app notes; all recommend diode-connected > > >transistors over diodes. > > > > > > > I don't care about ideality factor, how well a c-b junction might > > match some theoretical ideal-diode equation. What matters is how well > > you calibrate the V-T curve of a device, and how similar later devices > > might be. > > I've no quarrel with that. If you're going to individually calibrate the > sensor anyhow, any diode will do and ideality doesn't matter.
For kicks, I took 6 irf520 (N-chan fet) stuck 'em to a hunk of copper, near each other. Shorted G to S (after one measured zero volts) and used my DMM to measure the body diode. 0.5893 0.5880 0.5887 0.5890 0.5887 0.5887 That's not too bad. There must be loads on the web about using the fet body diode as a temp sensor. George H.
> > It seems the advantage of a diode-connected transistor is being repeatable > and interchangeable /without/ calibration. Which is what George wants, AIUI. > > Cheers, > James Arthur
On Tue, 27 Jun 2017 11:49:51 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Tuesday, June 27, 2017 at 12:51:20 PM UTC-4, John Larkin wrote: >> On Tue, 27 Jun 2017 09:12:14 -0700 (PDT), George Herold >> <gherold@teachspin.com> wrote: >> >> >On Tuesday, June 27, 2017 at 10:02:22 AM UTC-4, John Larkin wrote: >> >> On Mon, 26 Jun 2017 18:02:21 -0700 (PDT), dagmargoodboat@yahoo.com >> >> wrote: >> >> >> >> >On Monday, June 26, 2017 at 8:17:45 PM UTC-4, dagmarg...@yahoo.com wrote: >> >> >> On Monday, June 26, 2017 at 5:33:47 PM UTC-4, John Larkin wrote: >> >> >> > On Mon, 26 Jun 2017 14:21:43 -0700 (PDT), dagmargoodboat@yahoo.com >> >> >> > wrote: >> >> >> > >> >> >> > >On Monday, June 26, 2017 at 1:15:44 PM UTC-4, John Larkin wrote: >> >> >> > >> On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), dagmargoodboat@yahoo.com >> >> >> > >> wrote: >> >> >> > >> >> >> >> > >> >On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: >> >> >> > >> >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: >> >> >> > >> >> > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) >> >> >> > >> >> > There's a couple of depletion fets in series as current limiters. (LND150) >> >> >> > >> >> > The b-e junction starts to zener at ~30 V (only two tested so far). >> >> >> > >> >> > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? >> >> >> > >> >> > Will it take time? I'm going to measure forward voltage again after >> >> >> > >> >> > zenering for 15 minutes. Should I measure something else too? >> >> >> > >> >> > >> >> >> > >> >> > TIA >> >> >> > >> >> > >> >> >> > >> >> > George H. >> >> >> > >> >> >> >> >> > >> >> Why not just protect your TIP31C from zenering? A few diodes would do it. >> >> >> > >> >> >> >> >> > >> > >> >> >> > >> >e.g., >> >> >> > >> > | >> >> >> > >> > +----. >> >> >> > >> > | | >> >> >> > >> >TIP31C |<' --- >> >> >> > >> > .---| ^ D1 >> >> >> > >> > | |\ | >> >> >> > >> > | | | >> >> >> > >> > '-----+----' >> >> >> > >> > | >> >> >> > >> > | >> >> >> > >> > >> >> >> > >> >Add a zener in series with D1 if you need to stand off some reverse voltage. >> >> >> > >> > >> >> >> > >> >Cheers, >> >> >> > >> >James Arthur >> >> >> > >> >> >> >> > >> Or use the c-b junction instead. >> >> >> > > >> >> >> > >That loses the transistor action, degrading its temperature-sensing >> >> >> > >performance. >> >> >> > > >> >> >> > >Cheers, >> >> >> > >James Arthur >> >> >> > >> >> >> > Think so? It's still a diode with a roughly -2 mV/K tempco. >> >> >> >> >> >> I read that ages ago, in an early article about using Motorola transistors >> >> >> specifically spec'd as temperature sensors IIRC. (It's amazing I can >> >> >> remember that. Still have the article somewhere, I'm sure.) >> >> >> >> >> >> > No transistor will ever be a super-accurate temp sensor. >> >> >> >> >> >> Delta Vbe is good pretty easily to +/-1oC, uncalibrated. >> >> >> >> >> >> > There is an LM35 available in TO220. >> >> >> > >> >> >> > Zetex makes a cool 1K ohm SOT23 nickel RTD too. Nickel is cool because >> >> >> > the curve slopes up, so you can linearize it by just loading it. RTDs >> >> >> > are tough and don't rectify RF or oscillate. >> >> >> >> >> >> Can't argue with RTDs... >> >> >> >> >> >This has interesting measurements of a variety of vendors' 2n3904's: >> >> > >> >> >http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf >> >> > >> >> > "Figure 2 also shows why true 2-terminal discrete diodes >> >> > are not used in temperature sensing applications instead >> >> > of 3-terminal devices such as the 2N3904. >> >> > >> >> > A discrete 2-terminal diode, ideally, would perform in >> >> > temperature sensing applications as well as a thermal >> >> > diode would. However, characterization in the labs >> >> > determined that discrete 2-terminal diodes typically >> >> > have an ideality factor much higher (1.2&#2013266070;1.5) than >> >> > ? ASSUMED of 1.004. This discrepancy (between ? ASSUMED >> >> > and ? REAL) would cause unacceptable temperature >> >> > measurement errors at all temperatures." >> >> >> >> "Unacceptable" is arbitrary and judgemental. It's kinda prissy, going >> >> around assuming stuff. >> >> >> >> > >> >> >I just read a number delta Vbe app notes; all recommend diode-connected >> >> >transistors over diodes. >> >> > >> >> >Cheers, >> >> >James Arthur >> >> >> >> I don't care about ideality factor, how well a c-b junction might >> >> match some theoretical ideal-diode equation. What matters is how well >> >> you calibrate the V-T curve of a device, and how similar later devices >> >> might be. >> > >> >I sorta agree, If I could find a diode that was repeatable and easily >> >calibrated against some standard that would be fine. >> >> Buy the transistors from the same vendor, no matter how you process >> the signals. Ideally, but a reel that's a lifetime supply. >> >> Seems to me that you can't avoid some actual temperature measurements, >> unless you buy an IC or an RTD that has guaranteed specs. >> >> >> > >> >The one nice thing about the 'ideal' behavior is that you can check the >> >calibration (very roughly) by looking at the signal as a function of bias >> >current. That nice.. and also nice physics. >> > >> >George h. >> >> In your production units, are you planning to do the theoretical >> delta-I/deltaV math, or are you just going to use a constant current >> and measure the diode voltage drop? >For production, I measure a temperature* and a voltage drop at CC. >And then generate a table of V vs T. >I tell them about the delta I/ delta V thing.. I'm guessing most everyone >just ignores it, it's only EE geek types that like that kind of thing. >> >> How accurate do you need it to be? >Right, one degree (C or K) is plenty good for most things. >Resolution, and changes in temperature are more important. > >George H. >*I've got a calibrated diode from lakeshore, which is my temperature >'standard'. I tack that onto the transistor.
Cryo stuff? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Tuesday, June 27, 2017 at 3:32:48 PM UTC-4, John Larkin wrote:
> On Tue, 27 Jun 2017 11:49:51 -0700 (PDT), George Herold > <gherold@teachspin.com> wrote: > > >On Tuesday, June 27, 2017 at 12:51:20 PM UTC-4, John Larkin wrote: > >> On Tue, 27 Jun 2017 09:12:14 -0700 (PDT), George Herold > >> <gherold@teachspin.com> wrote: > >> > >> >On Tuesday, June 27, 2017 at 10:02:22 AM UTC-4, John Larkin wrote: > >> >> On Mon, 26 Jun 2017 18:02:21 -0700 (PDT), dagmargoodboat@yahoo.com > >> >> wrote: > >> >> > >> >> >On Monday, June 26, 2017 at 8:17:45 PM UTC-4, dagmarg...@yahoo.com wrote: > >> >> >> On Monday, June 26, 2017 at 5:33:47 PM UTC-4, John Larkin wrote: > >> >> >> > On Mon, 26 Jun 2017 14:21:43 -0700 (PDT), dagmargoodboat@yahoo.com > >> >> >> > wrote: > >> >> >> > > >> >> >> > >On Monday, June 26, 2017 at 1:15:44 PM UTC-4, John Larkin wrote: > >> >> >> > >> On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), dagmargoodboat@yahoo.com > >> >> >> > >> wrote: > >> >> >> > >> > >> >> >> > >> >On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: > >> >> >> > >> >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: > >> >> >> > >> >> > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) > >> >> >> > >> >> > There's a couple of depletion fets in series as current limiters. (LND150) > >> >> >> > >> >> > The b-e junction starts to zener at ~30 V (only two tested so far). > >> >> >> > >> >> > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? > >> >> >> > >> >> > Will it take time? I'm going to measure forward voltage again after > >> >> >> > >> >> > zenering for 15 minutes. Should I measure something else too? > >> >> >> > >> >> > > >> >> >> > >> >> > TIA > >> >> >> > >> >> > > >> >> >> > >> >> > George H. > >> >> >> > >> >> > >> >> >> > >> >> Why not just protect your TIP31C from zenering? A few diodes would do it. > >> >> >> > >> >> > >> >> >> > >> > > >> >> >> > >> >e.g., > >> >> >> > >> > | > >> >> >> > >> > +----. > >> >> >> > >> > | | > >> >> >> > >> >TIP31C |<' --- > >> >> >> > >> > .---| ^ D1 > >> >> >> > >> > | |\ | > >> >> >> > >> > | | | > >> >> >> > >> > '-----+----' > >> >> >> > >> > | > >> >> >> > >> > | > >> >> >> > >> > > >> >> >> > >> >Add a zener in series with D1 if you need to stand off some reverse voltage. > >> >> >> > >> > > >> >> >> > >> >Cheers, > >> >> >> > >> >James Arthur > >> >> >> > >> > >> >> >> > >> Or use the c-b junction instead. > >> >> >> > > > >> >> >> > >That loses the transistor action, degrading its temperature-sensing > >> >> >> > >performance. > >> >> >> > > > >> >> >> > >Cheers, > >> >> >> > >James Arthur > >> >> >> > > >> >> >> > Think so? It's still a diode with a roughly -2 mV/K tempco. > >> >> >> > >> >> >> I read that ages ago, in an early article about using Motorola transistors > >> >> >> specifically spec'd as temperature sensors IIRC. (It's amazing I can > >> >> >> remember that. Still have the article somewhere, I'm sure.) > >> >> >> > >> >> >> > No transistor will ever be a super-accurate temp sensor. > >> >> >> > >> >> >> Delta Vbe is good pretty easily to +/-1oC, uncalibrated. > >> >> >> > >> >> >> > There is an LM35 available in TO220. > >> >> >> > > >> >> >> > Zetex makes a cool 1K ohm SOT23 nickel RTD too. Nickel is cool because > >> >> >> > the curve slopes up, so you can linearize it by just loading it. RTDs > >> >> >> > are tough and don't rectify RF or oscillate. > >> >> >> > >> >> >> Can't argue with RTDs... > >> >> >> > >> >> >This has interesting measurements of a variety of vendors' 2n3904's: > >> >> > > >> >> >http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf > >> >> > > >> >> > "Figure 2 also shows why true 2-terminal discrete diodes > >> >> > are not used in temperature sensing applications instead > >> >> > of 3-terminal devices such as the 2N3904. > >> >> > > >> >> > A discrete 2-terminal diode, ideally, would perform in > >> >> > temperature sensing applications as well as a thermal > >> >> > diode would. However, characterization in the labs > >> >> > determined that discrete 2-terminal diodes typically > >> >> > have an ideality factor much higher (1.2&ndash;1.5) than > >> >> > ? ASSUMED of 1.004. This discrepancy (between ? ASSUMED > >> >> > and ? REAL) would cause unacceptable temperature > >> >> > measurement errors at all temperatures." > >> >> > >> >> "Unacceptable" is arbitrary and judgemental. It's kinda prissy, going > >> >> around assuming stuff. > >> >> > >> >> > > >> >> >I just read a number delta Vbe app notes; all recommend diode-connected > >> >> >transistors over diodes. > >> >> > > >> >> >Cheers, > >> >> >James Arthur > >> >> > >> >> I don't care about ideality factor, how well a c-b junction might > >> >> match some theoretical ideal-diode equation. What matters is how well > >> >> you calibrate the V-T curve of a device, and how similar later devices > >> >> might be. > >> > > >> >I sorta agree, If I could find a diode that was repeatable and easily > >> >calibrated against some standard that would be fine. > >> > >> Buy the transistors from the same vendor, no matter how you process > >> the signals. Ideally, but a reel that's a lifetime supply. > >> > >> Seems to me that you can't avoid some actual temperature measurements, > >> unless you buy an IC or an RTD that has guaranteed specs. > >> > >> > >> > > >> >The one nice thing about the 'ideal' behavior is that you can check the > >> >calibration (very roughly) by looking at the signal as a function of bias > >> >current. That nice.. and also nice physics. > >> > > >> >George h. > >> > >> In your production units, are you planning to do the theoretical > >> delta-I/deltaV math, or are you just going to use a constant current > >> and measure the diode voltage drop? > >For production, I measure a temperature* and a voltage drop at CC. > >And then generate a table of V vs T. > >I tell them about the delta I/ delta V thing.. I'm guessing most everyone > >just ignores it, it's only EE geek types that like that kind of thing. > >> > >> How accurate do you need it to be? > >Right, one degree (C or K) is plenty good for most things. > >Resolution, and changes in temperature are more important. > > > >George H. > >*I've got a calibrated diode from lakeshore, which is my temperature > >'standard'. I tack that onto the transistor. > > Cryo stuff?
Right, 77- 400 K. The diode connected transistor is going to 'crap out' somewhere below 77 K. Well it will still be a diode but no 'gain' from the collector.
> > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
On Tuesday, June 27, 2017 at 1:31:43 PM UTC-4, Jim Thompson wrote:
> On Tue, 27 Jun 2017 10:11:48 -0700 (PDT), dagmargoodboat@yahoo.com > wrote: > > [snip] > > > >That, or use the delta Vbe technique (take the Vbe at two currents, then > >subtract to get the difference). > > > [snip] > > Page AN45-7 > > <http://www.analog-innovations.com/SED/Measurements_Including_TemperatureSensors_JimWilliams_AN45_.pdf> > > which I've successively implemented on several custom chips (with > embellished mirrors and switching).
Yes, thanks. I originally saw that in EDN, I think, where it had a better write-up. I used the technique to stabilize a smoke detector design once. I think it might have been &ldquo;Transistor Sensor Needs No Compensation,&rdquo; Jim Williams, EDN, April 25, 1991, but I can't find it just now. (Update: Okay, I found it. That was the article, but I don't notice any textual differences between that and the file you posted.) Woodward has a three-current version to reduce ohmic errors. http://www.electronicdesign.com/analog/triple-current-modulation-delta-vsubbesub-thermometry-cancels-ohmic-error-sources Here are some more of the app notes I scanned through yesterday... AN137 - Accurate Temperature Sensing with an External P-N Junction http://cds.linear.com/docs/en/application-note/an137f.pdf AND8494 - Thermal Sensing Methods used in ON Semiconductor Devices https://www.onsemi.com/pub/Collateral/AND8494-D.PDF AN10349 Digital temperature sensor accuracy explained http://www.nxp.com/docs/en/application-note/AN10349.pdf AN12.14 Remote Thermal Sensing Diode Selection Guide http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf Cheers, James Arthur
On Tue, 27 Jun 2017 12:47:15 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

>On Tuesday, June 27, 2017 at 1:31:43 PM UTC-4, Jim Thompson wrote: >> On Tue, 27 Jun 2017 10:11:48 -0700 (PDT), dagmargoodboat@yahoo.com >> wrote: >> >> [snip] >> > >> >That, or use the delta Vbe technique (take the Vbe at two currents, then >> >subtract to get the difference). >> > >> [snip] >> >> Page AN45-7 >> >> <http://www.analog-innovations.com/SED/Measurements_Including_TemperatureSensors_JimWilliams_AN45_.pdf> >> >> which I've successively implemented on several custom chips (with >> embellished mirrors and switching). > >Yes, thanks. I originally saw that in EDN, I think, where it had a better >write-up. I used the technique to stabilize a smoke detector design once. > > I think it might have been &#2013266067;Transistor Sensor Needs No Compensation,&#2013266068; >Jim Williams, EDN, April 25, 1991, but I can't find it just now. > >(Update: Okay, I found it. That was the article, but I don't notice any >textual differences between that and the file you posted.) > > Woodward has a three-current version to reduce ohmic errors. > http://www.electronicdesign.com/analog/triple-current-modulation-delta-vsubbesub-thermometry-cancels-ohmic-error-sources > >Here are some more of the app notes I scanned through yesterday... > > AN137 - Accurate Temperature Sensing with an External P-N Junction > http://cds.linear.com/docs/en/application-note/an137f.pdf > > AND8494 - Thermal Sensing Methods used in ON Semiconductor Devices > https://www.onsemi.com/pub/Collateral/AND8494-D.PDF > > AN10349 Digital temperature sensor accuracy explained > http://www.nxp.com/docs/en/application-note/AN10349.pdf > > AN12.14 Remote Thermal Sensing Diode Selection Guide > http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf > >Cheers, >James Arthur
Thanks for all those nice links! I collect such things... you never know when such a need will arise. Many of these schemes, difficult in a discrete implementation, are a piece-a-cake in my custom chip world ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website. Thinking outside the box... producing elegant solutions.
On Tue, 27 Jun 2017 12:41:18 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Tuesday, June 27, 2017 at 3:32:48 PM UTC-4, John Larkin wrote: >> On Tue, 27 Jun 2017 11:49:51 -0700 (PDT), George Herold >> <gherold@teachspin.com> wrote: >> >> >On Tuesday, June 27, 2017 at 12:51:20 PM UTC-4, John Larkin wrote: >> >> On Tue, 27 Jun 2017 09:12:14 -0700 (PDT), George Herold >> >> <gherold@teachspin.com> wrote: >> >> >> >> >On Tuesday, June 27, 2017 at 10:02:22 AM UTC-4, John Larkin wrote: >> >> >> On Mon, 26 Jun 2017 18:02:21 -0700 (PDT), dagmargoodboat@yahoo.com >> >> >> wrote: >> >> >> >> >> >> >On Monday, June 26, 2017 at 8:17:45 PM UTC-4, dagmarg...@yahoo.com wrote: >> >> >> >> On Monday, June 26, 2017 at 5:33:47 PM UTC-4, John Larkin wrote: >> >> >> >> > On Mon, 26 Jun 2017 14:21:43 -0700 (PDT), dagmargoodboat@yahoo.com >> >> >> >> > wrote: >> >> >> >> > >> >> >> >> > >On Monday, June 26, 2017 at 1:15:44 PM UTC-4, John Larkin wrote: >> >> >> >> > >> On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), dagmargoodboat@yahoo.com >> >> >> >> > >> wrote: >> >> >> >> > >> >> >> >> >> > >> >On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: >> >> >> >> > >> >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: >> >> >> >> > >> >> > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) >> >> >> >> > >> >> > There's a couple of depletion fets in series as current limiters. (LND150) >> >> >> >> > >> >> > The b-e junction starts to zener at ~30 V (only two tested so far). >> >> >> >> > >> >> > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? >> >> >> >> > >> >> > Will it take time? I'm going to measure forward voltage again after >> >> >> >> > >> >> > zenering for 15 minutes. Should I measure something else too? >> >> >> >> > >> >> > >> >> >> >> > >> >> > TIA >> >> >> >> > >> >> > >> >> >> >> > >> >> > George H. >> >> >> >> > >> >> >> >> >> >> > >> >> Why not just protect your TIP31C from zenering? A few diodes would do it. >> >> >> >> > >> >> >> >> >> >> > >> > >> >> >> >> > >> >e.g., >> >> >> >> > >> > | >> >> >> >> > >> > +----. >> >> >> >> > >> > | | >> >> >> >> > >> >TIP31C |<' --- >> >> >> >> > >> > .---| ^ D1 >> >> >> >> > >> > | |\ | >> >> >> >> > >> > | | | >> >> >> >> > >> > '-----+----' >> >> >> >> > >> > | >> >> >> >> > >> > | >> >> >> >> > >> > >> >> >> >> > >> >Add a zener in series with D1 if you need to stand off some reverse voltage. >> >> >> >> > >> > >> >> >> >> > >> >Cheers, >> >> >> >> > >> >James Arthur >> >> >> >> > >> >> >> >> >> > >> Or use the c-b junction instead. >> >> >> >> > > >> >> >> >> > >That loses the transistor action, degrading its temperature-sensing >> >> >> >> > >performance. >> >> >> >> > > >> >> >> >> > >Cheers, >> >> >> >> > >James Arthur >> >> >> >> > >> >> >> >> > Think so? It's still a diode with a roughly -2 mV/K tempco. >> >> >> >> >> >> >> >> I read that ages ago, in an early article about using Motorola transistors >> >> >> >> specifically spec'd as temperature sensors IIRC. (It's amazing I can >> >> >> >> remember that. Still have the article somewhere, I'm sure.) >> >> >> >> >> >> >> >> > No transistor will ever be a super-accurate temp sensor. >> >> >> >> >> >> >> >> Delta Vbe is good pretty easily to +/-1oC, uncalibrated. >> >> >> >> >> >> >> >> > There is an LM35 available in TO220. >> >> >> >> > >> >> >> >> > Zetex makes a cool 1K ohm SOT23 nickel RTD too. Nickel is cool because >> >> >> >> > the curve slopes up, so you can linearize it by just loading it. RTDs >> >> >> >> > are tough and don't rectify RF or oscillate. >> >> >> >> >> >> >> >> Can't argue with RTDs... >> >> >> >> >> >> >> >This has interesting measurements of a variety of vendors' 2n3904's: >> >> >> > >> >> >> >http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf >> >> >> > >> >> >> > "Figure 2 also shows why true 2-terminal discrete diodes >> >> >> > are not used in temperature sensing applications instead >> >> >> > of 3-terminal devices such as the 2N3904. >> >> >> > >> >> >> > A discrete 2-terminal diode, ideally, would perform in >> >> >> > temperature sensing applications as well as a thermal >> >> >> > diode would. However, characterization in the labs >> >> >> > determined that discrete 2-terminal diodes typically >> >> >> > have an ideality factor much higher (1.2&#2013266070;1.5) than >> >> >> > ? ASSUMED of 1.004. This discrepancy (between ? ASSUMED >> >> >> > and ? REAL) would cause unacceptable temperature >> >> >> > measurement errors at all temperatures." >> >> >> >> >> >> "Unacceptable" is arbitrary and judgemental. It's kinda prissy, going >> >> >> around assuming stuff. >> >> >> >> >> >> > >> >> >> >I just read a number delta Vbe app notes; all recommend diode-connected >> >> >> >transistors over diodes. >> >> >> > >> >> >> >Cheers, >> >> >> >James Arthur >> >> >> >> >> >> I don't care about ideality factor, how well a c-b junction might >> >> >> match some theoretical ideal-diode equation. What matters is how well >> >> >> you calibrate the V-T curve of a device, and how similar later devices >> >> >> might be. >> >> > >> >> >I sorta agree, If I could find a diode that was repeatable and easily >> >> >calibrated against some standard that would be fine. >> >> >> >> Buy the transistors from the same vendor, no matter how you process >> >> the signals. Ideally, but a reel that's a lifetime supply. >> >> >> >> Seems to me that you can't avoid some actual temperature measurements, >> >> unless you buy an IC or an RTD that has guaranteed specs. >> >> >> >> >> >> > >> >> >The one nice thing about the 'ideal' behavior is that you can check the >> >> >calibration (very roughly) by looking at the signal as a function of bias >> >> >current. That nice.. and also nice physics. >> >> > >> >> >George h. >> >> >> >> In your production units, are you planning to do the theoretical >> >> delta-I/deltaV math, or are you just going to use a constant current >> >> and measure the diode voltage drop? >> >For production, I measure a temperature* and a voltage drop at CC. >> >And then generate a table of V vs T. >> >I tell them about the delta I/ delta V thing.. I'm guessing most everyone >> >just ignores it, it's only EE geek types that like that kind of thing. >> >> >> >> How accurate do you need it to be? >> >Right, one degree (C or K) is plenty good for most things. >> >Resolution, and changes in temperature are more important. >> > >> >George H. >> >*I've got a calibrated diode from lakeshore, which is my temperature >> >'standard'. I tack that onto the transistor. >> >> Cryo stuff? >Right, 77- 400 K. The diode connected transistor is going to >'crap out' somewhere below 77 K. Well it will still be a diode >but no 'gain' from the collector.
77K should be OK. Bipolar devices, transistors and diodes, go to hell below around 20K. Lakeshore has some magical recipe that makes repeatable temperature measurement diodes at liquid helium temps, but it's not easy. Other people have messed up at this. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Tuesday, June 27, 2017 at 3:59:08 PM UTC-4, John Larkin wrote:
> On Tue, 27 Jun 2017 12:41:18 -0700 (PDT), George Herold > <gherold@teachspin.com> wrote: > > >On Tuesday, June 27, 2017 at 3:32:48 PM UTC-4, John Larkin wrote: > >> On Tue, 27 Jun 2017 11:49:51 -0700 (PDT), George Herold > >> <gherold@teachspin.com> wrote: > >> > >> >On Tuesday, June 27, 2017 at 12:51:20 PM UTC-4, John Larkin wrote: > >> >> On Tue, 27 Jun 2017 09:12:14 -0700 (PDT), George Herold > >> >> <gherold@teachspin.com> wrote: > >> >> > >> >> >On Tuesday, June 27, 2017 at 10:02:22 AM UTC-4, John Larkin wrote: > >> >> >> On Mon, 26 Jun 2017 18:02:21 -0700 (PDT), dagmargoodboat@yahoo.com > >> >> >> wrote: > >> >> >> > >> >> >> >On Monday, June 26, 2017 at 8:17:45 PM UTC-4, dagmarg...@yahoo.com wrote: > >> >> >> >> On Monday, June 26, 2017 at 5:33:47 PM UTC-4, John Larkin wrote: > >> >> >> >> > On Mon, 26 Jun 2017 14:21:43 -0700 (PDT), dagmargoodboat@yahoo.com > >> >> >> >> > wrote: > >> >> >> >> > > >> >> >> >> > >On Monday, June 26, 2017 at 1:15:44 PM UTC-4, John Larkin wrote: > >> >> >> >> > >> On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), dagmargoodboat@yahoo.com > >> >> >> >> > >> wrote: > >> >> >> >> > >> > >> >> >> >> > >> >On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: > >> >> >> >> > >> >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: > >> >> >> >> > >> >> > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) > >> >> >> >> > >> >> > There's a couple of depletion fets in series as current limiters. (LND150) > >> >> >> >> > >> >> > The b-e junction starts to zener at ~30 V (only two tested so far). > >> >> >> >> > >> >> > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? > >> >> >> >> > >> >> > Will it take time? I'm going to measure forward voltage again after > >> >> >> >> > >> >> > zenering for 15 minutes. Should I measure something else too? > >> >> >> >> > >> >> > > >> >> >> >> > >> >> > TIA > >> >> >> >> > >> >> > > >> >> >> >> > >> >> > George H. > >> >> >> >> > >> >> > >> >> >> >> > >> >> Why not just protect your TIP31C from zenering? A few diodes would do it. > >> >> >> >> > >> >> > >> >> >> >> > >> > > >> >> >> >> > >> >e.g., > >> >> >> >> > >> > | > >> >> >> >> > >> > +----. > >> >> >> >> > >> > | | > >> >> >> >> > >> >TIP31C |<' --- > >> >> >> >> > >> > .---| ^ D1 > >> >> >> >> > >> > | |\ | > >> >> >> >> > >> > | | | > >> >> >> >> > >> > '-----+----' > >> >> >> >> > >> > | > >> >> >> >> > >> > | > >> >> >> >> > >> > > >> >> >> >> > >> >Add a zener in series with D1 if you need to stand off some reverse voltage. > >> >> >> >> > >> > > >> >> >> >> > >> >Cheers, > >> >> >> >> > >> >James Arthur > >> >> >> >> > >> > >> >> >> >> > >> Or use the c-b junction instead. > >> >> >> >> > > > >> >> >> >> > >That loses the transistor action, degrading its temperature-sensing > >> >> >> >> > >performance. > >> >> >> >> > > > >> >> >> >> > >Cheers, > >> >> >> >> > >James Arthur > >> >> >> >> > > >> >> >> >> > Think so? It's still a diode with a roughly -2 mV/K tempco. > >> >> >> >> > >> >> >> >> I read that ages ago, in an early article about using Motorola transistors > >> >> >> >> specifically spec'd as temperature sensors IIRC. (It's amazing I can > >> >> >> >> remember that. Still have the article somewhere, I'm sure.) > >> >> >> >> > >> >> >> >> > No transistor will ever be a super-accurate temp sensor. > >> >> >> >> > >> >> >> >> Delta Vbe is good pretty easily to +/-1oC, uncalibrated. > >> >> >> >> > >> >> >> >> > There is an LM35 available in TO220. > >> >> >> >> > > >> >> >> >> > Zetex makes a cool 1K ohm SOT23 nickel RTD too. Nickel is cool because > >> >> >> >> > the curve slopes up, so you can linearize it by just loading it. RTDs > >> >> >> >> > are tough and don't rectify RF or oscillate. > >> >> >> >> > >> >> >> >> Can't argue with RTDs... > >> >> >> >> > >> >> >> >This has interesting measurements of a variety of vendors' 2n3904's: > >> >> >> > > >> >> >> >http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf > >> >> >> > > >> >> >> > "Figure 2 also shows why true 2-terminal discrete diodes > >> >> >> > are not used in temperature sensing applications instead > >> >> >> > of 3-terminal devices such as the 2N3904. > >> >> >> > > >> >> >> > A discrete 2-terminal diode, ideally, would perform in > >> >> >> > temperature sensing applications as well as a thermal > >> >> >> > diode would. However, characterization in the labs > >> >> >> > determined that discrete 2-terminal diodes typically > >> >> >> > have an ideality factor much higher (1.2&ndash;1.5) than > >> >> >> > ? ASSUMED of 1.004. This discrepancy (between ? ASSUMED > >> >> >> > and ? REAL) would cause unacceptable temperature > >> >> >> > measurement errors at all temperatures." > >> >> >> > >> >> >> "Unacceptable" is arbitrary and judgemental. It's kinda prissy, going > >> >> >> around assuming stuff. > >> >> >> > >> >> >> > > >> >> >> >I just read a number delta Vbe app notes; all recommend diode-connected > >> >> >> >transistors over diodes. > >> >> >> > > >> >> >> >Cheers, > >> >> >> >James Arthur > >> >> >> > >> >> >> I don't care about ideality factor, how well a c-b junction might > >> >> >> match some theoretical ideal-diode equation. What matters is how well > >> >> >> you calibrate the V-T curve of a device, and how similar later devices > >> >> >> might be. > >> >> > > >> >> >I sorta agree, If I could find a diode that was repeatable and easily > >> >> >calibrated against some standard that would be fine. > >> >> > >> >> Buy the transistors from the same vendor, no matter how you process > >> >> the signals. Ideally, but a reel that's a lifetime supply. > >> >> > >> >> Seems to me that you can't avoid some actual temperature measurements, > >> >> unless you buy an IC or an RTD that has guaranteed specs. > >> >> > >> >> > >> >> > > >> >> >The one nice thing about the 'ideal' behavior is that you can check the > >> >> >calibration (very roughly) by looking at the signal as a function of bias > >> >> >current. That nice.. and also nice physics. > >> >> > > >> >> >George h. > >> >> > >> >> In your production units, are you planning to do the theoretical > >> >> delta-I/deltaV math, or are you just going to use a constant current > >> >> and measure the diode voltage drop? > >> >For production, I measure a temperature* and a voltage drop at CC. > >> >And then generate a table of V vs T. > >> >I tell them about the delta I/ delta V thing.. I'm guessing most everyone > >> >just ignores it, it's only EE geek types that like that kind of thing. > >> >> > >> >> How accurate do you need it to be? > >> >Right, one degree (C or K) is plenty good for most things. > >> >Resolution, and changes in temperature are more important. > >> > > >> >George H. > >> >*I've got a calibrated diode from lakeshore, which is my temperature > >> >'standard'. I tack that onto the transistor. > >> > >> Cryo stuff? > >Right, 77- 400 K. The diode connected transistor is going to > >'crap out' somewhere below 77 K. Well it will still be a diode > >but no 'gain' from the collector. > > 77K should be OK. Bipolar devices, transistors and diodes, go to hell > below around 20K. > > Lakeshore has some magical recipe that makes repeatable temperature > measurement diodes at liquid helium temps, but it's not easy. Other > people have messed up at this.
Hmm OK, I have no liquid helium here. So I can't do tests below 77K. It'd be fun to look at commercial diodes at low temps... maybe find one that works. (Is there really a special sauce at Lakeshore?) George H.
> > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
On Tue, 27 Jun 2017 13:34:07 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Tuesday, June 27, 2017 at 3:59:08 PM UTC-4, John Larkin wrote: >> On Tue, 27 Jun 2017 12:41:18 -0700 (PDT), George Herold >> <gherold@teachspin.com> wrote: >> >> >On Tuesday, June 27, 2017 at 3:32:48 PM UTC-4, John Larkin wrote: >> >> On Tue, 27 Jun 2017 11:49:51 -0700 (PDT), George Herold >> >> <gherold@teachspin.com> wrote: >> >> >> >> >On Tuesday, June 27, 2017 at 12:51:20 PM UTC-4, John Larkin wrote: >> >> >> On Tue, 27 Jun 2017 09:12:14 -0700 (PDT), George Herold >> >> >> <gherold@teachspin.com> wrote: >> >> >> >> >> >> >On Tuesday, June 27, 2017 at 10:02:22 AM UTC-4, John Larkin wrote: >> >> >> >> On Mon, 26 Jun 2017 18:02:21 -0700 (PDT), dagmargoodboat@yahoo.com >> >> >> >> wrote: >> >> >> >> >> >> >> >> >On Monday, June 26, 2017 at 8:17:45 PM UTC-4, dagmarg...@yahoo.com wrote: >> >> >> >> >> On Monday, June 26, 2017 at 5:33:47 PM UTC-4, John Larkin wrote: >> >> >> >> >> > On Mon, 26 Jun 2017 14:21:43 -0700 (PDT), dagmargoodboat@yahoo.com >> >> >> >> >> > wrote: >> >> >> >> >> > >> >> >> >> >> > >On Monday, June 26, 2017 at 1:15:44 PM UTC-4, John Larkin wrote: >> >> >> >> >> > >> On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), dagmargoodboat@yahoo.com >> >> >> >> >> > >> wrote: >> >> >> >> >> > >> >> >> >> >> >> > >> >On Monday, June 26, 2017 at 12:59:50 PM UTC-4, dagmarg...@yahoo.com wrote: >> >> >> >> >> > >> >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George Herold wrote: >> >> >> >> >> > >> >> > I'm using a TIP31C (pnp in to-220 pac) as a temp sensor (diode connected) >> >> >> >> >> > >> >> > There's a couple of depletion fets in series as current limiters. (LND150) >> >> >> >> >> > >> >> > The b-e junction starts to zener at ~30 V (only two tested so far). >> >> >> >> >> > >> >> > So I've got ~1.5 mA flowing at 30 V. Is this going to damage the junction? >> >> >> >> >> > >> >> > Will it take time? I'm going to measure forward voltage again after >> >> >> >> >> > >> >> > zenering for 15 minutes. Should I measure something else too? >> >> >> >> >> > >> >> > >> >> >> >> >> > >> >> > TIA >> >> >> >> >> > >> >> > >> >> >> >> >> > >> >> > George H. >> >> >> >> >> > >> >> >> >> >> >> >> > >> >> Why not just protect your TIP31C from zenering? A few diodes would do it. >> >> >> >> >> > >> >> >> >> >> >> >> > >> > >> >> >> >> >> > >> >e.g., >> >> >> >> >> > >> > | >> >> >> >> >> > >> > +----. >> >> >> >> >> > >> > | | >> >> >> >> >> > >> >TIP31C |<' --- >> >> >> >> >> > >> > .---| ^ D1 >> >> >> >> >> > >> > | |\ | >> >> >> >> >> > >> > | | | >> >> >> >> >> > >> > '-----+----' >> >> >> >> >> > >> > | >> >> >> >> >> > >> > | >> >> >> >> >> > >> > >> >> >> >> >> > >> >Add a zener in series with D1 if you need to stand off some reverse voltage. >> >> >> >> >> > >> > >> >> >> >> >> > >> >Cheers, >> >> >> >> >> > >> >James Arthur >> >> >> >> >> > >> >> >> >> >> >> > >> Or use the c-b junction instead. >> >> >> >> >> > > >> >> >> >> >> > >That loses the transistor action, degrading its temperature-sensing >> >> >> >> >> > >performance. >> >> >> >> >> > > >> >> >> >> >> > >Cheers, >> >> >> >> >> > >James Arthur >> >> >> >> >> > >> >> >> >> >> > Think so? It's still a diode with a roughly -2 mV/K tempco. >> >> >> >> >> >> >> >> >> >> I read that ages ago, in an early article about using Motorola transistors >> >> >> >> >> specifically spec'd as temperature sensors IIRC. (It's amazing I can >> >> >> >> >> remember that. Still have the article somewhere, I'm sure.) >> >> >> >> >> >> >> >> >> >> > No transistor will ever be a super-accurate temp sensor. >> >> >> >> >> >> >> >> >> >> Delta Vbe is good pretty easily to +/-1oC, uncalibrated. >> >> >> >> >> >> >> >> >> >> > There is an LM35 available in TO220. >> >> >> >> >> > >> >> >> >> >> > Zetex makes a cool 1K ohm SOT23 nickel RTD too. Nickel is cool because >> >> >> >> >> > the curve slopes up, so you can linearize it by just loading it. RTDs >> >> >> >> >> > are tough and don't rectify RF or oscillate. >> >> >> >> >> >> >> >> >> >> Can't argue with RTDs... >> >> >> >> >> >> >> >> >> >This has interesting measurements of a variety of vendors' 2n3904's: >> >> >> >> > >> >> >> >> >http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf >> >> >> >> > >> >> >> >> > "Figure 2 also shows why true 2-terminal discrete diodes >> >> >> >> > are not used in temperature sensing applications instead >> >> >> >> > of 3-terminal devices such as the 2N3904. >> >> >> >> > >> >> >> >> > A discrete 2-terminal diode, ideally, would perform in >> >> >> >> > temperature sensing applications as well as a thermal >> >> >> >> > diode would. However, characterization in the labs >> >> >> >> > determined that discrete 2-terminal diodes typically >> >> >> >> > have an ideality factor much higher (1.2&#2013266070;1.5) than >> >> >> >> > ? ASSUMED of 1.004. This discrepancy (between ? ASSUMED >> >> >> >> > and ? REAL) would cause unacceptable temperature >> >> >> >> > measurement errors at all temperatures." >> >> >> >> >> >> >> >> "Unacceptable" is arbitrary and judgemental. It's kinda prissy, going >> >> >> >> around assuming stuff. >> >> >> >> >> >> >> >> > >> >> >> >> >I just read a number delta Vbe app notes; all recommend diode-connected >> >> >> >> >transistors over diodes. >> >> >> >> > >> >> >> >> >Cheers, >> >> >> >> >James Arthur >> >> >> >> >> >> >> >> I don't care about ideality factor, how well a c-b junction might >> >> >> >> match some theoretical ideal-diode equation. What matters is how well >> >> >> >> you calibrate the V-T curve of a device, and how similar later devices >> >> >> >> might be. >> >> >> > >> >> >> >I sorta agree, If I could find a diode that was repeatable and easily >> >> >> >calibrated against some standard that would be fine. >> >> >> >> >> >> Buy the transistors from the same vendor, no matter how you process >> >> >> the signals. Ideally, but a reel that's a lifetime supply. >> >> >> >> >> >> Seems to me that you can't avoid some actual temperature measurements, >> >> >> unless you buy an IC or an RTD that has guaranteed specs. >> >> >> >> >> >> >> >> >> > >> >> >> >The one nice thing about the 'ideal' behavior is that you can check the >> >> >> >calibration (very roughly) by looking at the signal as a function of bias >> >> >> >current. That nice.. and also nice physics. >> >> >> > >> >> >> >George h. >> >> >> >> >> >> In your production units, are you planning to do the theoretical >> >> >> delta-I/deltaV math, or are you just going to use a constant current >> >> >> and measure the diode voltage drop? >> >> >For production, I measure a temperature* and a voltage drop at CC. >> >> >And then generate a table of V vs T. >> >> >I tell them about the delta I/ delta V thing.. I'm guessing most everyone >> >> >just ignores it, it's only EE geek types that like that kind of thing. >> >> >> >> >> >> How accurate do you need it to be? >> >> >Right, one degree (C or K) is plenty good for most things. >> >> >Resolution, and changes in temperature are more important. >> >> > >> >> >George H. >> >> >*I've got a calibrated diode from lakeshore, which is my temperature >> >> >'standard'. I tack that onto the transistor. >> >> >> >> Cryo stuff? >> >Right, 77- 400 K. The diode connected transistor is going to >> >'crap out' somewhere below 77 K. Well it will still be a diode >> >but no 'gain' from the collector. >> >> 77K should be OK. Bipolar devices, transistors and diodes, go to hell >> below around 20K. >> >> Lakeshore has some magical recipe that makes repeatable temperature >> measurement diodes at liquid helium temps, but it's not easy. Other >> people have messed up at this. >Hmm OK, I have no liquid helium here. So I can't do tests below 77K. >It'd be fun to look at commercial diodes at low temps... maybe find >one that works. (Is there really a special sauce at Lakeshore?) > >George H.
Below 20K, diode voltage drop skyrockets (to, like, volts at a couple K) and things get ohmic. Apparently it's erratic on doping or something, because other people have tried to compete with Lakeshore and every batch was different. We did the cryo instrumentation for the Jlabs/CEBAF machine, and for the helium liquefaction plant for the Supercollider (which may still be there.) -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
"George Herold" <gherold@teachspin.com> wrote in message 
news:19ba65c7-d8d1-4a14-9e82-ae7dac32a491@googlegroups.com...
On Tuesday, June 27, 2017 at 3:59:08 PM UTC-4, John Larkin wrote:
> On Tue, 27 Jun 2017 12:41:18 -0700 (PDT), George Herold > <gherold@teachspin.com> wrote: > > >On Tuesday, June 27, 2017 at 3:32:48 PM UTC-4, John Larkin wrote: > >> On Tue, 27 Jun 2017 11:49:51 -0700 (PDT), George Herold > >> <gherold@teachspin.com> wrote: > >> > >> >On Tuesday, June 27, 2017 at 12:51:20 PM UTC-4, John Larkin wrote: > >> >> On Tue, 27 Jun 2017 09:12:14 -0700 (PDT), George Herold > >> >> <gherold@teachspin.com> wrote: > >> >> > >> >> >On Tuesday, June 27, 2017 at 10:02:22 AM UTC-4, John Larkin wrote: > >> >> >> On Mon, 26 Jun 2017 18:02:21 -0700 (PDT), > >> >> >> dagmargoodboat@yahoo.com > >> >> >> wrote: > >> >> >> > >> >> >> >On Monday, June 26, 2017 at 8:17:45 PM UTC-4, > >> >> >> >dagmarg...@yahoo.com wrote: > >> >> >> >> On Monday, June 26, 2017 at 5:33:47 PM UTC-4, John Larkin > >> >> >> >> wrote: > >> >> >> >> > On Mon, 26 Jun 2017 14:21:43 -0700 (PDT), > >> >> >> >> > dagmargoodboat@yahoo.com > >> >> >> >> > wrote: > >> >> >> >> > > >> >> >> >> > >On Monday, June 26, 2017 at 1:15:44 PM UTC-4, John Larkin > >> >> >> >> > >wrote: > >> >> >> >> > >> On Mon, 26 Jun 2017 10:04:35 -0700 (PDT), > >> >> >> >> > >> dagmargoodboat@yahoo.com > >> >> >> >> > >> wrote: > >> >> >> >> > >> > >> >> >> >> > >> >On Monday, June 26, 2017 at 12:59:50 PM UTC-4, > >> >> >> >> > >> >dagmarg...@yahoo.com wrote: > >> >> >> >> > >> >> On Monday, June 26, 2017 at 11:51:45 AM UTC-4, George > >> >> >> >> > >> >> Herold wrote: > >> >> >> >> > >> >> > I'm using a TIP31C (pnp in to-220 pac) as a temp > >> >> >> >> > >> >> > sensor (diode connected) > >> >> >> >> > >> >> > There's a couple of depletion fets in series as > >> >> >> >> > >> >> > current limiters. (LND150) > >> >> >> >> > >> >> > The b-e junction starts to zener at ~30 V (only two > >> >> >> >> > >> >> > tested so far). > >> >> >> >> > >> >> > So I've got ~1.5 mA flowing at 30 V. Is this going > >> >> >> >> > >> >> > to damage the junction? > >> >> >> >> > >> >> > Will it take time? I'm going to measure forward > >> >> >> >> > >> >> > voltage again after > >> >> >> >> > >> >> > zenering for 15 minutes. Should I measure something > >> >> >> >> > >> >> > else too? > >> >> >> >> > >> >> > > >> >> >> >> > >> >> > TIA > >> >> >> >> > >> >> > > >> >> >> >> > >> >> > George H. > >> >> >> >> > >> >> > >> >> >> >> > >> >> Why not just protect your TIP31C from zenering? A few > >> >> >> >> > >> >> diodes would do it. > >> >> >> >> > >> >> > >> >> >> >> > >> > > >> >> >> >> > >> >e.g., > >> >> >> >> > >> > | > >> >> >> >> > >> > +----. > >> >> >> >> > >> > | | > >> >> >> >> > >> >TIP31C |<' --- > >> >> >> >> > >> > .---| ^ D1 > >> >> >> >> > >> > | |\ | > >> >> >> >> > >> > | | | > >> >> >> >> > >> > '-----+----' > >> >> >> >> > >> > | > >> >> >> >> > >> > | > >> >> >> >> > >> > > >> >> >> >> > >> >Add a zener in series with D1 if you need to stand off > >> >> >> >> > >> >some reverse voltage. > >> >> >> >> > >> > > >> >> >> >> > >> >Cheers, > >> >> >> >> > >> >James Arthur > >> >> >> >> > >> > >> >> >> >> > >> Or use the c-b junction instead. > >> >> >> >> > > > >> >> >> >> > >That loses the transistor action, degrading its > >> >> >> >> > >temperature-sensing > >> >> >> >> > >performance. > >> >> >> >> > > > >> >> >> >> > >Cheers, > >> >> >> >> > >James Arthur > >> >> >> >> > > >> >> >> >> > Think so? It's still a diode with a roughly -2 mV/K tempco. > >> >> >> >> > >> >> >> >> I read that ages ago, in an early article about using Motorola > >> >> >> >> transistors > >> >> >> >> specifically spec'd as temperature sensors IIRC. (It's amazing > >> >> >> >> I can > >> >> >> >> remember that. Still have the article somewhere, I'm sure.) > >> >> >> >> > >> >> >> >> > No transistor will ever be a super-accurate temp sensor. > >> >> >> >> > >> >> >> >> Delta Vbe is good pretty easily to +/-1oC, uncalibrated. > >> >> >> >> > >> >> >> >> > There is an LM35 available in TO220. > >> >> >> >> > > >> >> >> >> > Zetex makes a cool 1K ohm SOT23 nickel RTD too. Nickel is > >> >> >> >> > cool because > >> >> >> >> > the curve slopes up, so you can linearize it by just loading > >> >> >> >> > it. RTDs > >> >> >> >> > are tough and don't rectify RF or oscillate. > >> >> >> >> > >> >> >> >> Can't argue with RTDs... > >> >> >> >> > >> >> >> >This has interesting measurements of a variety of vendors' > >> >> >> >2n3904's: > >> >> >> > > >> >> >> >http://ww1.microchip.com/downloads/en/AppNotes/00001838A.pdf > >> >> >> > > >> >> >> > "Figure 2 also shows why true 2-terminal discrete diodes > >> >> >> > are not used in temperature sensing applications instead > >> >> >> > of 3-terminal devices such as the 2N3904. > >> >> >> > > >> >> >> > A discrete 2-terminal diode, ideally, would perform in > >> >> >> > temperature sensing applications as well as a thermal > >> >> >> > diode would. However, characterization in the labs > >> >> >> > determined that discrete 2-terminal diodes typically > >> >> >> > have an ideality factor much higher (1.2-1.5) than > >> >> >> > ? ASSUMED of 1.004. This discrepancy (between ? ASSUMED > >> >> >> > and ? REAL) would cause unacceptable temperature > >> >> >> > measurement errors at all temperatures." > >> >> >> > >> >> >> "Unacceptable" is arbitrary and judgemental. It's kinda prissy, > >> >> >> going > >> >> >> around assuming stuff. > >> >> >> > >> >> >> > > >> >> >> >I just read a number delta Vbe app notes; all recommend > >> >> >> >diode-connected > >> >> >> >transistors over diodes. > >> >> >> > > >> >> >> >Cheers, > >> >> >> >James Arthur > >> >> >> > >> >> >> I don't care about ideality factor, how well a c-b junction might > >> >> >> match some theoretical ideal-diode equation. What matters is how > >> >> >> well > >> >> >> you calibrate the V-T curve of a device, and how similar later > >> >> >> devices > >> >> >> might be. > >> >> > > >> >> >I sorta agree, If I could find a diode that was repeatable and > >> >> >easily > >> >> >calibrated against some standard that would be fine. > >> >> > >> >> Buy the transistors from the same vendor, no matter how you process > >> >> the signals. Ideally, but a reel that's a lifetime supply. > >> >> > >> >> Seems to me that you can't avoid some actual temperature > >> >> measurements, > >> >> unless you buy an IC or an RTD that has guaranteed specs. > >> >> > >> >> > >> >> > > >> >> >The one nice thing about the 'ideal' behavior is that you can check > >> >> >the > >> >> >calibration (very roughly) by looking at the signal as a function > >> >> >of bias > >> >> >current. That nice.. and also nice physics. > >> >> > > >> >> >George h. > >> >> > >> >> In your production units, are you planning to do the theoretical > >> >> delta-I/deltaV math, or are you just going to use a constant current > >> >> and measure the diode voltage drop? > >> >For production, I measure a temperature* and a voltage drop at CC. > >> >And then generate a table of V vs T. > >> >I tell them about the delta I/ delta V thing.. I'm guessing most > >> >everyone > >> >just ignores it, it's only EE geek types that like that kind of thing. > >> >> > >> >> How accurate do you need it to be? > >> >Right, one degree (C or K) is plenty good for most things. > >> >Resolution, and changes in temperature are more important. > >> > > >> >George H. > >> >*I've got a calibrated diode from lakeshore, which is my temperature > >> >'standard'. I tack that onto the transistor. > >> > >> Cryo stuff? > >Right, 77- 400 K. The diode connected transistor is going to > >'crap out' somewhere below 77 K. Well it will still be a diode > >but no 'gain' from the collector. > > 77K should be OK. Bipolar devices, transistors and diodes, go to hell > below around 20K. > > Lakeshore has some magical recipe that makes repeatable temperature > measurement diodes at liquid helium temps, but it's not easy. Other > people have messed up at this.
Hmm OK, I have no liquid helium here. So I can't do tests below 77K. It'd be fun to look at commercial diodes at low temps... maybe find one that works. (Is there really a special sauce at Lakeshore?) George H.
> > > --
Pull a vacuum on the LN2 and it will go colder than 77K.