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.What does your temp/voltage conditioning circuit look like?
Zenering a big transistor
Started by ●June 26, 2017
Reply by ●June 26, 20172017-06-26
Reply by ●June 26, 20172017-06-26
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
Reply by ●June 26, 20172017-06-26
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 ArthurThink so? It's still a diode with a roughly -2 mV/K tempco. No transistor will ever be a super-accurate temp sensor. 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. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●June 26, 20172017-06-26
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... Cheers, James Arthur
Reply by ●June 26, 20172017-06-26
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 η ASSUMED of 1.004. This discrepancy (between η ASSUMED and η REAL) would cause unacceptable temperature measurement errors at all temperatures." I just read a number delta Vbe app notes; all recommend diode-connected transistors over diodes. Cheers, James Arthur
Reply by ●June 27, 20172017-06-27
On Monday, June 26, 2017 at 2:33:47 PM UTC-7, John Larkin 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)> No transistor will ever be a super-accurate temp sensor. > > There is an LM35 available in TO220.Eh? LM35 IS a transistor used as a temp sensor (with linearizing tricks and a preamplifier). Software is just as good at linearizing, and a transistor makes a very good sensor. The same equation-of-operation that makes the LM35 massproducible applies to all low-noise transistors (and with some bias precautions, almost all bipolars). I'd recommend against using germanium, though.
Reply by ●June 27, 20172017-06-27
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 ArthurI 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. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●June 27, 20172017-06-27
On Mon, 26 Jun 2017 20:56:56 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:>On Monday, June 26, 2017 at 2:33:47 PM UTC-7, John Larkin 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) > > >> No transistor will ever be a super-accurate temp sensor. >> >> There is an LM35 available in TO220. > >Eh?Have a hearing problem? I could type louder. LM35 IS a transistor used as a temp sensor (with linearizing>tricks and a preamplifier).It's a modified bandgap reference. And it's specified for temperature sensing accuracy. Software is just as good at linearizing,>and a transistor makes a very good sensor.A transistor sensor will not be calibrated. The LM35 does have some bugs, though.> >The same equation-of-operation that makes the LM35 massproducible >applies to all low-noise transistors (and with some bias precautions, >almost all bipolars). I'd recommend against using germanium, though.-- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●June 27, 20172017-06-27
John Larkin wrote:> Reference zeners are stable to parts per million for years.BTW, LTZ1000 used in the most demanding applications (8.5 digit voltameters) is defined as super-stable and has even a built-in heater. But its application note contains some resistors and even an opamp on the most critical path. How then were they able to achieve that microvolt per 10V accuracy with all that junk in between? Best regards, Piotr
Reply by ●June 27, 20172017-06-27
On Monday, June 26, 2017 at 9:02:31 PM UTC-4, dagmarg...@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 > η ASSUMED of 1.004. This discrepancy (between η ASSUMED > and η REAL) would cause unacceptable temperature > measurement errors at all temperatures." > > I just read a number delta Vbe app notes; all recommend diode-connected > transistors over diodes. > > Cheers, > James ArthurThat's a nice paper. Do they say how they get the ideality factor? I've got data (at different currents) for the tip32 and the error is ~3 K if I assume fidelity factor = 1. Changing it to 1.003 (or so) would make the numbers better. BTW here's a plot/table for tip32 at 10 uA of current. https://www.dropbox.com/s/qxxoamj2hcn2nly/Diode%20calibration%20table.doc?dl=0 George H.
