On Monday, 11 February 2013 13:42:01 UTC-5, Phil Hobbs wrote:> Hi, all--I'm looking for a curve tracer. Ideally it would be > > USB-powered, and come with software that would make plots and generate > > data files. Nothing too fancy, just I_C and I_B vs V_CE and V_BE, and > > the equivalent for FETs. A plus would be automatic computation of beta, > > V_GSth, Early voltage, and even some of the DC SPICE parameters like > > emitter and base resistance. > > > > It would be especially nice if it could measure gate current with a > > resolution of a picoamp or less. > > > > Any suggestions? > > > > Cheers > > > > Phil Hobbs > > > > -- > > Dr Philip C D Hobbs > > Principal Consultant > > ElectroOptical Innovations LLC > > Optics, Electro-optics, Photonics, Analog Electronics > > > > 160 North State Road #203 > > Briarcliff Manor NY 10510 > > > > hobbs at electrooptical dot net > > http://electrooptical.netAgilent has a USB curve tracer offering, but needless to say it costs a lot more than the Anatek gizmo, and does not offer pA resolution. Search on U2722A. James
Curve tracers
Started by ●February 11, 2013
Reply by ●February 13, 20132013-02-13
Reply by ●February 13, 20132013-02-13
On 2/13/2013 12:27 PM, John Larkin wrote:> On Wed, 13 Feb 2013 11:34:36 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 2/13/2013 11:30 AM, John Larkin wrote: >>> On Wed, 13 Feb 2013 11:01:28 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 2/13/2013 10:24 AM, John Larkin wrote: >>>>> On Tue, 12 Feb 2013 21:57:13 -0800, josephkk <joseph_barrett@sbcglobal.net> >>>>> wrote: >>>>> >>>>>> On Tue, 12 Feb 2013 11:59:36 -0500, Phil Hobbs >>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>> >>>>>>> On 02/11/2013 05:29 PM, mike wrote: >>>>>>>> On 2/11/2013 10:42 AM, Phil Hobbs wrote: >>>>>>>>> Hi, all--I'm looking for a curve tracer. Ideally it would be >>>>>>>>> USB-powered, and come with software that would make plots and generate >>>>>>>>> data files. Nothing too fancy, just I_C and I_B vs V_CE and V_BE, and >>>>>>>>> the equivalent for FETs. A plus would be automatic computation of beta, >>>>>>>>> V_GSth, Early voltage, and even some of the DC SPICE parameters like >>>>>>>>> emitter and base resistance. >>>>>>>>> >>>>>>>>> It would be especially nice if it could measure gate current with a >>>>>>>>> resolution of a picoamp or less. >>>>>>>>> >>>>>>>>> Any suggestions? >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>>> >>>>>>>> You're asking a LOT. >>>>>>>> >>>>>>>> A curve tracer is a qualitative measurement device. >>>>>>>> I use a TEK 7CT1N for simple stuff and only drag out the 576 >>>>>>>> when I gotta have it. I use it more for blowing shorts >>>>>>>> out of NiCd's than for testing transistors. >>>>>>> >>>>>>> It's only qualitative because it only has a CRT readout. A curve tracer >>>>>>> is a sort of stripped-down version of a semiconductor parameter analyzer >>>>>>> such as an HP4145B, which is very quantitative indeed. (I wouldn't mind >>>>>>> one of those--I used to have one at my PPOE, but it takes a lot of rack >>>>>>> space.) >>>>>>>> >>>>>>>> If you try to make one using a series of fixed measurements >>>>>>>> and graphing them, you get mixed results. I tried that back in the day. >>>>>>>> The device thermal time constants significantly affect the measurement >>>>>>>> details. >>>>>>> >>>>>>> Yup. You have to be quick about it if you're dissipating any >>>>>>> significant power. Of course with a MCU and DACs, you can do the >>>>>>> measurements out of order to keep the average dissipation constant. >>>>>>> >>>>>>>> >>>>>>>> And the parasitics of the test fixture swamp device parasitics, unless you >>>>>>>> use network analyzer fixturing. >>>>>>> >>>>>>> Not necessarily. My Boonton 72BD easily measures a few femtofarads. >>>>>>> You just null it out before attaching the hot lead to the device. >>>>>>> >>>>>>>> >>>>>>>> Picoamps to amps is a wide dynamic range and will require some serious >>>>>>>> attention to range switching. >>>>>>>> >>>>>>>> Not saying it can't be done, just that it's not nearly as simple as it >>>>>>>> sounds. >>>>>>> >>>>>>> I don't need amps--I'd be quite happy with a 50-100 mA top end. Most of >>>>>>> what I need a curve tracer for is measuring weird RF devices with lousy >>>>>>> datasheets. >>>>>>> >>>>>>> Cheers >>>>>>> >>>>>>> Phil Hobbs >>>>>> >>>>>> Oh foo, the fixturing for RF devices can get really weird and expensive. >>>>>> Those will be on you if we get together and create a USB curve tracer. >>>>>> >>>>>> ?-) >>>>> >>>>> The problem with a lot of (most) RF devices is their terrible DC >>>>> characterization. Like, no DC curves at all. The s-params give you a rough idea >>>>> of the high-speed behavior. >>>>> >>>>> RF data sheets often say to just adjust the bias until it works. The specified >>>>> breakdown voltage specs are not useful, because sometimes they assume, without >>>>> saying so, that the drain voltage can swing to multiples of the supply voltage, >>>>> and factor that in. Parts spec'd at 6 volts can cheerfully avalanche at 25. A >>>>> detector diode might be spec'd a 2 volts reverse, woth no curves at all, because >>>>> they figure that's all a detector user needs to know. >>>> >>>> I'm normally working down on the low frequency end anyway, e.g. a 100 >>>> MHz biochip front end using 14-GHz pHEMTs and 40-GHz bipolars, so simple >>>> concepts like C_JC and R_BB' still work OK. Boontons rule! >>> >>> Right. You have to make your own curves, like C-vs-V. That's why a USB >>> curve tracer should measure capacitances, too. >>> >>> Heck, somebody here with a curve tracer and a Booonton could set up a >>> garage operation to characterize parts for a fee. Modelithics does >>> that for big bucks. >>> >>> >> >> Have you measured the leakage of the Boonton's biasing system? Maybe >> one could just hang a little board on the back of one, and do it that way. >> >> Cheers >> >> Phil Hobbs > > Good idea. Design the USB curve tracer to run through a Boonton 72 to > get the capacitances. The Boonton has an analog output on the back. > But it would be more fun to do it ourselves. > >Sure, I'm in. Do you think it might actually sell? Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 USA +1 845 480 2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●February 13, 20132013-02-13
On Wed, 13 Feb 2013 13:41:34 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 2/13/2013 12:27 PM, John Larkin wrote: >> On Wed, 13 Feb 2013 11:34:36 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 2/13/2013 11:30 AM, John Larkin wrote: >>>> On Wed, 13 Feb 2013 11:01:28 -0500, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> On 2/13/2013 10:24 AM, John Larkin wrote: >>>>>> On Tue, 12 Feb 2013 21:57:13 -0800, josephkk <joseph_barrett@sbcglobal.net> >>>>>> wrote: >>>>>> >>>>>>> On Tue, 12 Feb 2013 11:59:36 -0500, Phil Hobbs >>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>> >>>>>>>> On 02/11/2013 05:29 PM, mike wrote: >>>>>>>>> On 2/11/2013 10:42 AM, Phil Hobbs wrote: >>>>>>>>>> Hi, all--I'm looking for a curve tracer. Ideally it would be >>>>>>>>>> USB-powered, and come with software that would make plots and generate >>>>>>>>>> data files. Nothing too fancy, just I_C and I_B vs V_CE and V_BE, and >>>>>>>>>> the equivalent for FETs. A plus would be automatic computation of beta, >>>>>>>>>> V_GSth, Early voltage, and even some of the DC SPICE parameters like >>>>>>>>>> emitter and base resistance. >>>>>>>>>> >>>>>>>>>> It would be especially nice if it could measure gate current with a >>>>>>>>>> resolution of a picoamp or less. >>>>>>>>>> >>>>>>>>>> Any suggestions? >>>>>>>>>> >>>>>>>>>> Cheers >>>>>>>>>> >>>>>>>>>> Phil Hobbs >>>>>>>>>> >>>>>>>>> You're asking a LOT. >>>>>>>>> >>>>>>>>> A curve tracer is a qualitative measurement device. >>>>>>>>> I use a TEK 7CT1N for simple stuff and only drag out the 576 >>>>>>>>> when I gotta have it. I use it more for blowing shorts >>>>>>>>> out of NiCd's than for testing transistors. >>>>>>>> >>>>>>>> It's only qualitative because it only has a CRT readout. A curve tracer >>>>>>>> is a sort of stripped-down version of a semiconductor parameter analyzer >>>>>>>> such as an HP4145B, which is very quantitative indeed. (I wouldn't mind >>>>>>>> one of those--I used to have one at my PPOE, but it takes a lot of rack >>>>>>>> space.) >>>>>>>>> >>>>>>>>> If you try to make one using a series of fixed measurements >>>>>>>>> and graphing them, you get mixed results. I tried that back in the day. >>>>>>>>> The device thermal time constants significantly affect the measurement >>>>>>>>> details. >>>>>>>> >>>>>>>> Yup. You have to be quick about it if you're dissipating any >>>>>>>> significant power. Of course with a MCU and DACs, you can do the >>>>>>>> measurements out of order to keep the average dissipation constant. >>>>>>>> >>>>>>>>> >>>>>>>>> And the parasitics of the test fixture swamp device parasitics, unless you >>>>>>>>> use network analyzer fixturing. >>>>>>>> >>>>>>>> Not necessarily. My Boonton 72BD easily measures a few femtofarads. >>>>>>>> You just null it out before attaching the hot lead to the device. >>>>>>>> >>>>>>>>> >>>>>>>>> Picoamps to amps is a wide dynamic range and will require some serious >>>>>>>>> attention to range switching. >>>>>>>>> >>>>>>>>> Not saying it can't be done, just that it's not nearly as simple as it >>>>>>>>> sounds. >>>>>>>> >>>>>>>> I don't need amps--I'd be quite happy with a 50-100 mA top end. Most of >>>>>>>> what I need a curve tracer for is measuring weird RF devices with lousy >>>>>>>> datasheets. >>>>>>>> >>>>>>>> Cheers >>>>>>>> >>>>>>>> Phil Hobbs >>>>>>> >>>>>>> Oh foo, the fixturing for RF devices can get really weird and expensive. >>>>>>> Those will be on you if we get together and create a USB curve tracer. >>>>>>> >>>>>>> ?-) >>>>>> >>>>>> The problem with a lot of (most) RF devices is their terrible DC >>>>>> characterization. Like, no DC curves at all. The s-params give you a rough idea >>>>>> of the high-speed behavior. >>>>>> >>>>>> RF data sheets often say to just adjust the bias until it works. The specified >>>>>> breakdown voltage specs are not useful, because sometimes they assume, without >>>>>> saying so, that the drain voltage can swing to multiples of the supply voltage, >>>>>> and factor that in. Parts spec'd at 6 volts can cheerfully avalanche at 25. A >>>>>> detector diode might be spec'd a 2 volts reverse, woth no curves at all, because >>>>>> they figure that's all a detector user needs to know. >>>>> >>>>> I'm normally working down on the low frequency end anyway, e.g. a 100 >>>>> MHz biochip front end using 14-GHz pHEMTs and 40-GHz bipolars, so simple >>>>> concepts like C_JC and R_BB' still work OK. Boontons rule! >>>> >>>> Right. You have to make your own curves, like C-vs-V. That's why a USB >>>> curve tracer should measure capacitances, too. >>>> >>>> Heck, somebody here with a curve tracer and a Booonton could set up a >>>> garage operation to characterize parts for a fee. Modelithics does >>>> that for big bucks. >>>> >>>> >>> >>> Have you measured the leakage of the Boonton's biasing system? Maybe >>> one could just hang a little board on the back of one, and do it that way. >>> >>> Cheers >>> >>> Phil Hobbs >> >> Good idea. Design the USB curve tracer to run through a Boonton 72 to >> get the capacitances. The Boonton has an analog output on the back. >> But it would be more fun to do it ourselves. >> >> > >Sure, I'm in. Do you think it might actually sell? >Well, some for sure. Ten a year? 200? Time to start scribbling. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Reply by ●February 13, 20132013-02-13
On Wed, 13 Feb 2013 11:16:46 -0800, John Larkin <jlarkin@highlandtechnology.com> wrote:><snip> >Well, some for sure. Ten a year? 200? > >Time to start scribbling.I'd be happy to volunteer embedded software work. Pretty much what I do is measurement instrumentation software and associated Windows software, where needed. For EM1 level: BF, BR, IS Measure ambient temperature near the BJT [and hold Vbc near 0 to avoid power dissipation as is assumed in EM1] and also require doing this at several ambient temperatures to get Eg and perhaps the power of T [nominally 3 in the IS(T) equation, but if allowed to change freely then becomes part of the curve fitting algorithm, which I can also write.] By the way, the Tek 577 achieves base currents of 5nA with the 177 porch. Not sure how low you'd like to achieve. For EM2 level: Ohmic re', rc', and rb'; Cjeo, Cjco, C-substrate; forward and reverse transit times; gradients for the EB and CB capacitances and their barrier potentials. Things aren't always straightword. If you attempt to measure re', for example, by driving known base currents and observing Vce (with open collector), there is a flyback effect caused by a decrease of BR at low currents which should be taken into account. The re' value is best gained as 1/slope near that flyback point than somewhere else on the curve. But not confused by the actual flyback itself. Jon
Reply by ●February 13, 20132013-02-13
On 2/13/2013 9:36 AM, Fred Abse wrote:> On Tue, 12 Feb 2013 15:30:25 -0800, mike wrote: > >> Methinks you're applying apples thinking to oranges. If you take a >> measurement at a fixed operating point, whether it be DC or pulsed, your >> average junction temperature is likely to be different from what it would >> be in an analog curve tracer like the 576. All those measurement points >> are not likely to line up on exactly the same line you'd see with an >> analog plot. Nothing wrong with that. If you want data at a particular >> operating point, that's the way to go. >> If you want a curve tracer, like it says in the subject line, you may not >> see what you expect. > > The basic 576 *incorporates* pulsed measurements, as well as swept. > 300 microseconds and 80 microseconds. Bottom row of buttons on the right > hand side. It does that at a single operating point at a time, if you want > a plot, you have to draw it by hand.You insist on talking about how a 576 works. I'm talking about the measurement you're making. If what you're measuring is what you want, you're good to go. If you want to DESIGN a curve tracer, you might want to be concerned with the relationship between what you measure and the picture on the display. For a qualitative display, it doesn't matter a lot. If you're reading out three digits of precision, you need to think about dynamic temperature effects. You can do it either way...just understand the difference.> > Methinks you are not that familiar with the 576. > I use one or other of the two in my lab on an almost daily basis.You have me beat. I have only one. I bow to your quantitative superiority. All I can tell you is that, back in the day, I tried to build a curve tracer that graphed static measurements. I didn't like the result and aborted the project. It was not as trivial as I thought.> > The 176 is an addon unit that fits in place of the standard test fixture, > that goes to 200 amps. It is pulsed mode only, using delay line charge > storage, to avoid enormous, heavy power supplies, unlike the 175, that > needed two people or a fork truck to carry it. >
Reply by ●February 13, 20132013-02-13
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message news:511BB8D8.5050602@electrooptical.net...> On 2/13/2013 10:24 AM, John Larkin wrote: >> On Tue, 12 Feb 2013 21:57:13 -0800, josephkk >> <joseph_barrett@sbcglobal.net> >> wrote: >> >>> On Tue, 12 Feb 2013 11:59:36 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 02/11/2013 05:29 PM, mike wrote: >>>>> On 2/11/2013 10:42 AM, Phil Hobbs wrote: >>>>>> Hi, all--I'm looking for a curve tracer. Ideally it would be >>>>>> USB-powered, and come with software that would make plots and >>>>>> generate >>>>>> data files. Nothing too fancy, just I_C and I_B vs V_CE and V_BE, and >>>>>> the equivalent for FETs. A plus would be automatic computation of >>>>>> beta, >>>>>> V_GSth, Early voltage, and even some of the DC SPICE parameters like >>>>>> emitter and base resistance. >>>>>> >>>>>> It would be especially nice if it could measure gate current with a >>>>>> resolution of a picoamp or less. >>>>>> >>>>>> Any suggestions? >>>>>> >>>>>> Cheers >>>>>> >>>>>> Phil Hobbs >>>>>> >>>>> You're asking a LOT. >>>>> >>>>> A curve tracer is a qualitative measurement device. >>>>> I use a TEK 7CT1N for simple stuff and only drag out the 576 >>>>> when I gotta have it. I use it more for blowing shorts >>>>> out of NiCd's than for testing transistors. >>>> >>>> It's only qualitative because it only has a CRT readout. A curve >>>> tracer >>>> is a sort of stripped-down version of a semiconductor parameter >>>> analyzer >>>> such as an HP4145B, which is very quantitative indeed. (I wouldn't >>>> mind >>>> one of those--I used to have one at my PPOE, but it takes a lot of rack >>>> space.) >>>>> >>>>> If you try to make one using a series of fixed measurements >>>>> and graphing them, you get mixed results. I tried that back in the >>>>> day. >>>>> The device thermal time constants significantly affect the measurement >>>>> details. >>>> >>>> Yup. You have to be quick about it if you're dissipating any >>>> significant power. Of course with a MCU and DACs, you can do the >>>> measurements out of order to keep the average dissipation constant. >>>> >>>>> >>>>> And the parasitics of the test fixture swamp device parasitics, unless >>>>> you >>>>> use network analyzer fixturing. >>>> >>>> Not necessarily. My Boonton 72BD easily measures a few femtofarads. >>>> You just null it out before attaching the hot lead to the device. >>>> >>>>> >>>>> Picoamps to amps is a wide dynamic range and will require some serious >>>>> attention to range switching. >>>>> >>>>> Not saying it can't be done, just that it's not nearly as simple as it >>>>> sounds. >>>> >>>> I don't need amps--I'd be quite happy with a 50-100 mA top end. Most >>>> of >>>> what I need a curve tracer for is measuring weird RF devices with lousy >>>> datasheets. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> Oh foo, the fixturing for RF devices can get really weird and expensive. >>> Those will be on you if we get together and create a USB curve tracer. >>> >>> ?-) >> >> The problem with a lot of (most) RF devices is their terrible DC >> characterization. Like, no DC curves at all. The s-params give you a >> rough idea >> of the high-speed behavior. >> >> RF data sheets often say to just adjust the bias until it works. The >> specified >> breakdown voltage specs are not useful, because sometimes they assume, >> without >> saying so, that the drain voltage can swing to multiples of the supply >> voltage, >> and factor that in. Parts spec'd at 6 volts can cheerfully avalanche at >> 25. A >> detector diode might be spec'd a 2 volts reverse, woth no curves at all, >> because >> they figure that's all a detector user needs to know. > > I'm normally working down on the low frequency end anyway, e.g. a 100 MHz > biochip front end using 14-GHz pHEMTs and 40-GHz bipolars, so simple > concepts like C_JC and R_BB' still work OK. Boontons rule! > > Cheers > > Phil Hobbs > > > --Hi Phil, Do you have the manual for the 72BD? regards
Reply by ●February 13, 20132013-02-13
"John Larkin" <jlarkin@highlandtechnology.com> wrote in message news:ovinh8p9ceiq6ua0qv0kc0ggkpus3ki3s6@4ax.com...> On Wed, 13 Feb 2013 11:34:36 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >>On 2/13/2013 11:30 AM, John Larkin wrote: >>> On Wed, 13 Feb 2013 11:01:28 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 2/13/2013 10:24 AM, John Larkin wrote: >>>>> On Tue, 12 Feb 2013 21:57:13 -0800, josephkk >>>>> <joseph_barrett@sbcglobal.net> >>>>> wrote: >>>>> >>>>>> On Tue, 12 Feb 2013 11:59:36 -0500, Phil Hobbs >>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>> >>>>>>> On 02/11/2013 05:29 PM, mike wrote: >>>>>>>> On 2/11/2013 10:42 AM, Phil Hobbs wrote: >>>>>>>>> Hi, all--I'm looking for a curve tracer. Ideally it would be >>>>>>>>> USB-powered, and come with software that would make plots and >>>>>>>>> generate >>>>>>>>> data files. Nothing too fancy, just I_C and I_B vs V_CE and V_BE, >>>>>>>>> and >>>>>>>>> the equivalent for FETs. A plus would be automatic computation of >>>>>>>>> beta, >>>>>>>>> V_GSth, Early voltage, and even some of the DC SPICE parameters >>>>>>>>> like >>>>>>>>> emitter and base resistance. >>>>>>>>> >>>>>>>>> It would be especially nice if it could measure gate current with >>>>>>>>> a >>>>>>>>> resolution of a picoamp or less. >>>>>>>>> >>>>>>>>> Any suggestions? >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>>> >>>>>>>> You're asking a LOT. >>>>>>>> >>>>>>>> A curve tracer is a qualitative measurement device. >>>>>>>> I use a TEK 7CT1N for simple stuff and only drag out the 576 >>>>>>>> when I gotta have it. I use it more for blowing shorts >>>>>>>> out of NiCd's than for testing transistors. >>>>>>> >>>>>>> It's only qualitative because it only has a CRT readout. A curve >>>>>>> tracer >>>>>>> is a sort of stripped-down version of a semiconductor parameter >>>>>>> analyzer >>>>>>> such as an HP4145B, which is very quantitative indeed. (I wouldn't >>>>>>> mind >>>>>>> one of those--I used to have one at my PPOE, but it takes a lot of >>>>>>> rack >>>>>>> space.) >>>>>>>> >>>>>>>> If you try to make one using a series of fixed measurements >>>>>>>> and graphing them, you get mixed results. I tried that back in the >>>>>>>> day. >>>>>>>> The device thermal time constants significantly affect the >>>>>>>> measurement >>>>>>>> details. >>>>>>> >>>>>>> Yup. You have to be quick about it if you're dissipating any >>>>>>> significant power. Of course with a MCU and DACs, you can do the >>>>>>> measurements out of order to keep the average dissipation constant. >>>>>>> >>>>>>>> >>>>>>>> And the parasitics of the test fixture swamp device parasitics, >>>>>>>> unless you >>>>>>>> use network analyzer fixturing. >>>>>>> >>>>>>> Not necessarily. My Boonton 72BD easily measures a few femtofarads. >>>>>>> You just null it out before attaching the hot lead to the device. >>>>>>> >>>>>>>> >>>>>>>> Picoamps to amps is a wide dynamic range and will require some >>>>>>>> serious >>>>>>>> attention to range switching. >>>>>>>> >>>>>>>> Not saying it can't be done, just that it's not nearly as simple as >>>>>>>> it >>>>>>>> sounds. >>>>>>> >>>>>>> I don't need amps--I'd be quite happy with a 50-100 mA top end. >>>>>>> Most of >>>>>>> what I need a curve tracer for is measuring weird RF devices with >>>>>>> lousy >>>>>>> datasheets. >>>>>>> >>>>>>> Cheers >>>>>>> >>>>>>> Phil Hobbs >>>>>> >>>>>> Oh foo, the fixturing for RF devices can get really weird and >>>>>> expensive. >>>>>> Those will be on you if we get together and create a USB curve >>>>>> tracer. >>>>>> >>>>>> ?-) >>>>> >>>>> The problem with a lot of (most) RF devices is their terrible DC >>>>> characterization. Like, no DC curves at all. The s-params give you a >>>>> rough idea >>>>> of the high-speed behavior. >>>>> >>>>> RF data sheets often say to just adjust the bias until it works. The >>>>> specified >>>>> breakdown voltage specs are not useful, because sometimes they assume, >>>>> without >>>>> saying so, that the drain voltage can swing to multiples of the supply >>>>> voltage, >>>>> and factor that in. Parts spec'd at 6 volts can cheerfully avalanche >>>>> at 25. A >>>>> detector diode might be spec'd a 2 volts reverse, woth no curves at >>>>> all, because >>>>> they figure that's all a detector user needs to know. >>>> >>>> I'm normally working down on the low frequency end anyway, e.g. a 100 >>>> MHz biochip front end using 14-GHz pHEMTs and 40-GHz bipolars, so >>>> simple >>>> concepts like C_JC and R_BB' still work OK. Boontons rule! >>> >>> Right. You have to make your own curves, like C-vs-V. That's why a USB >>> curve tracer should measure capacitances, too. >>> >>> Heck, somebody here with a curve tracer and a Booonton could set up a >>> garage operation to characterize parts for a fee. Modelithics does >>> that for big bucks. >>> >>> >> >>Have you measured the leakage of the Boonton's biasing system? Maybe >>one could just hang a little board on the back of one, and do it that way. >> >>Cheers >> >>Phil Hobbs > > Good idea. Design the USB curve tracer to run through a Boonton 72 to > get the capacitances. The Boonton has an analog output on the back. > But it would be more fun to do it ourselves. > > > -- >The Boonton also outputs BCD on the rear connector.
Reply by ●February 13, 20132013-02-13
On 02/13/2013 03:38 PM, tm wrote:> > "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message > news:511BB8D8.5050602@electrooptical.net... >> On 2/13/2013 10:24 AM, John Larkin wrote: >>> On Tue, 12 Feb 2013 21:57:13 -0800, josephkk >>> <joseph_barrett@sbcglobal.net> >>> wrote: >>> >>>> On Tue, 12 Feb 2013 11:59:36 -0500, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> On 02/11/2013 05:29 PM, mike wrote: >>>>>> On 2/11/2013 10:42 AM, Phil Hobbs wrote: >>>>>>> Hi, all--I'm looking for a curve tracer. Ideally it would be >>>>>>> USB-powered, and come with software that would make plots and >>>>>>> generate >>>>>>> data files. Nothing too fancy, just I_C and I_B vs V_CE and V_BE, >>>>>>> and >>>>>>> the equivalent for FETs. A plus would be automatic computation of >>>>>>> beta, >>>>>>> V_GSth, Early voltage, and even some of the DC SPICE parameters like >>>>>>> emitter and base resistance. >>>>>>> >>>>>>> It would be especially nice if it could measure gate current with a >>>>>>> resolution of a picoamp or less. >>>>>>> >>>>>>> Any suggestions? >>>>>>> >>>>>>> Cheers >>>>>>> >>>>>>> Phil Hobbs >>>>>>> >>>>>> You're asking a LOT. >>>>>> >>>>>> A curve tracer is a qualitative measurement device. >>>>>> I use a TEK 7CT1N for simple stuff and only drag out the 576 >>>>>> when I gotta have it. I use it more for blowing shorts >>>>>> out of NiCd's than for testing transistors. >>>>> >>>>> It's only qualitative because it only has a CRT readout. A curve >>>>> tracer >>>>> is a sort of stripped-down version of a semiconductor parameter >>>>> analyzer >>>>> such as an HP4145B, which is very quantitative indeed. (I wouldn't >>>>> mind >>>>> one of those--I used to have one at my PPOE, but it takes a lot of >>>>> rack >>>>> space.) >>>>>> >>>>>> If you try to make one using a series of fixed measurements >>>>>> and graphing them, you get mixed results. I tried that back in the >>>>>> day. >>>>>> The device thermal time constants significantly affect the >>>>>> measurement >>>>>> details. >>>>> >>>>> Yup. You have to be quick about it if you're dissipating any >>>>> significant power. Of course with a MCU and DACs, you can do the >>>>> measurements out of order to keep the average dissipation constant. >>>>> >>>>>> >>>>>> And the parasitics of the test fixture swamp device parasitics, >>>>>> unless you >>>>>> use network analyzer fixturing. >>>>> >>>>> Not necessarily. My Boonton 72BD easily measures a few femtofarads. >>>>> You just null it out before attaching the hot lead to the device. >>>>> >>>>>> >>>>>> Picoamps to amps is a wide dynamic range and will require some >>>>>> serious >>>>>> attention to range switching. >>>>>> >>>>>> Not saying it can't be done, just that it's not nearly as simple >>>>>> as it >>>>>> sounds. >>>>> >>>>> I don't need amps--I'd be quite happy with a 50-100 mA top end. >>>>> Most of >>>>> what I need a curve tracer for is measuring weird RF devices with >>>>> lousy >>>>> datasheets. >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>> >>>> Oh foo, the fixturing for RF devices can get really weird and >>>> expensive. >>>> Those will be on you if we get together and create a USB curve tracer. >>>> >>>> ?-) >>> >>> The problem with a lot of (most) RF devices is their terrible DC >>> characterization. Like, no DC curves at all. The s-params give you a >>> rough idea >>> of the high-speed behavior. >>> >>> RF data sheets often say to just adjust the bias until it works. The >>> specified >>> breakdown voltage specs are not useful, because sometimes they >>> assume, without >>> saying so, that the drain voltage can swing to multiples of the >>> supply voltage, >>> and factor that in. Parts spec'd at 6 volts can cheerfully avalanche >>> at 25. A >>> detector diode might be spec'd a 2 volts reverse, woth no curves at >>> all, because >>> they figure that's all a detector user needs to know. >> >> I'm normally working down on the low frequency end anyway, e.g. a 100 >> MHz biochip front end using 14-GHz pHEMTs and 40-GHz bipolars, so >> simple concepts like C_JC and R_BB' still work OK. Boontons rule! >> >> Cheers >> >> Phil Hobbs >> >> >> -- > > Hi Phil, > > Do you have the manual for the 72BD? > > regardsI have a softcopy of the user's manual, but no service manual or schematics. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●February 13, 20132013-02-13
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message news:fZudnZV219rrmoHMnZ2dnUVZ_tudnZ2d@supernews.com...> On 02/13/2013 03:38 PM, tm wrote: >> >> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >> news:511BB8D8.5050602@electrooptical.net... >>> On 2/13/2013 10:24 AM, John Larkin wrote: >>>> On Tue, 12 Feb 2013 21:57:13 -0800, josephkk >>>> <joseph_barrett@sbcglobal.net> >>>> wrote: >>>> >>>>> On Tue, 12 Feb 2013 11:59:36 -0500, Phil Hobbs >>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>> >>>>>> On 02/11/2013 05:29 PM, mike wrote: >>>>>>> On 2/11/2013 10:42 AM, Phil Hobbs wrote: >>>>>>>> Hi, all--I'm looking for a curve tracer. Ideally it would be >>>>>>>> USB-powered, and come with software that would make plots and >>>>>>>> generate >>>>>>>> data files. Nothing too fancy, just I_C and I_B vs V_CE and V_BE, >>>>>>>> and >>>>>>>> the equivalent for FETs. A plus would be automatic computation of >>>>>>>> beta, >>>>>>>> V_GSth, Early voltage, and even some of the DC SPICE parameters >>>>>>>> like >>>>>>>> emitter and base resistance. >>>>>>>> >>>>>>>> It would be especially nice if it could measure gate current with a >>>>>>>> resolution of a picoamp or less. >>>>>>>> >>>>>>>> Any suggestions? >>>>>>>> >>>>>>>> Cheers >>>>>>>> >>>>>>>> Phil Hobbs >>>>>>>> >>>>>>> You're asking a LOT. >>>>>>> >>>>>>> A curve tracer is a qualitative measurement device. >>>>>>> I use a TEK 7CT1N for simple stuff and only drag out the 576 >>>>>>> when I gotta have it. I use it more for blowing shorts >>>>>>> out of NiCd's than for testing transistors. >>>>>> >>>>>> It's only qualitative because it only has a CRT readout. A curve >>>>>> tracer >>>>>> is a sort of stripped-down version of a semiconductor parameter >>>>>> analyzer >>>>>> such as an HP4145B, which is very quantitative indeed. (I wouldn't >>>>>> mind >>>>>> one of those--I used to have one at my PPOE, but it takes a lot of >>>>>> rack >>>>>> space.) >>>>>>> >>>>>>> If you try to make one using a series of fixed measurements >>>>>>> and graphing them, you get mixed results. I tried that back in the >>>>>>> day. >>>>>>> The device thermal time constants significantly affect the >>>>>>> measurement >>>>>>> details. >>>>>> >>>>>> Yup. You have to be quick about it if you're dissipating any >>>>>> significant power. Of course with a MCU and DACs, you can do the >>>>>> measurements out of order to keep the average dissipation constant. >>>>>> >>>>>>> >>>>>>> And the parasitics of the test fixture swamp device parasitics, >>>>>>> unless you >>>>>>> use network analyzer fixturing. >>>>>> >>>>>> Not necessarily. My Boonton 72BD easily measures a few femtofarads. >>>>>> You just null it out before attaching the hot lead to the device. >>>>>> >>>>>>> >>>>>>> Picoamps to amps is a wide dynamic range and will require some >>>>>>> serious >>>>>>> attention to range switching. >>>>>>> >>>>>>> Not saying it can't be done, just that it's not nearly as simple >>>>>>> as it >>>>>>> sounds. >>>>>> >>>>>> I don't need amps--I'd be quite happy with a 50-100 mA top end. >>>>>> Most of >>>>>> what I need a curve tracer for is measuring weird RF devices with >>>>>> lousy >>>>>> datasheets. >>>>>> >>>>>> Cheers >>>>>> >>>>>> Phil Hobbs >>>>> >>>>> Oh foo, the fixturing for RF devices can get really weird and >>>>> expensive. >>>>> Those will be on you if we get together and create a USB curve tracer. >>>>> >>>>> ?-) >>>> >>>> The problem with a lot of (most) RF devices is their terrible DC >>>> characterization. Like, no DC curves at all. The s-params give you a >>>> rough idea >>>> of the high-speed behavior. >>>> >>>> RF data sheets often say to just adjust the bias until it works. The >>>> specified >>>> breakdown voltage specs are not useful, because sometimes they >>>> assume, without >>>> saying so, that the drain voltage can swing to multiples of the >>>> supply voltage, >>>> and factor that in. Parts spec'd at 6 volts can cheerfully avalanche >>>> at 25. A >>>> detector diode might be spec'd a 2 volts reverse, woth no curves at >>>> all, because >>>> they figure that's all a detector user needs to know. >>> >>> I'm normally working down on the low frequency end anyway, e.g. a 100 >>> MHz biochip front end using 14-GHz pHEMTs and 40-GHz bipolars, so >>> simple concepts like C_JC and R_BB' still work OK. Boontons rule! >>> >>> Cheers >>> >>> Phil Hobbs >>> >>> >>> -- >> >> Hi Phil, >> >> Do you have the manual for the 72BD? >> >> regards > > I have a softcopy of the user's manual, but no service manual or > schematics. > > Cheers > > Phil Hobbs > > --If I find an electronic copy I'll let you know. tm
Reply by ●February 13, 20132013-02-13
On Wed, 13 Feb 2013 12:32:17 -0800, mike wrote:> If you're reading out three digits of precision, you need to think about > dynamic temperature effects.If you're reading three digits of precision, I would recommend reading the sheaf of application notes put out by Keithley on the subject of semiconductor characterization. It's decidedly nontrivial. -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
