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. 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. And the parasitics of the test fixture swamp device parasitics, unless you use network analyzer fixturing. 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.
Curve tracers
Started by ●February 11, 2013
Reply by ●February 11, 20132013-02-11
Reply by ●February 11, 20132013-02-11
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message news:PrCdnUXYCfPe94TMnZ2dnUVZ_qednZ2d@supernews.com...> On 02/11/2013 04:09 PM, John Larkin wrote: >> On Mon, 11 Feb 2013 13:42:01 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> 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 >> >> It should do capacitance too. I've been wanting to do one of these... >> I might if nobody else does it. >> >> > Capacitance would be nice, especially if it were done at medium frequency > a la Boonton, so that you could put in whatever ferrite beads and stuff > you needed to keep the DUT from oscillating. > > For my biochip front ends, I measure input capacitance by finding the gain > with a 1-pF input cap and a 100-pF, then looking at the change in gain to > find the voltage divider ratio. Not 100% kosher unless the feedback > capacitance is super low, but it has to be if one wants <~ 1 pF input > capacitances in a built-up circuit. > > Cheers > > Phil Hobbs > > --This might be worth $24 to explore. Needs +/- 15 volts and a XY scope. http://www.ebay.com/itm/140547987228?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
Reply by ●February 11, 20132013-02-11
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 >A digital scope works well for that, it can be connected to the PC. You only need to create a test jig ramp signal that the scope can trigger on. One could write the PC software and maybe even use a USB IO dongle to control the test jig for various operations. Jamie
Reply by ●February 11, 20132013-02-11
On Mon, 11 Feb 2013 14:14:25 -0800, Joerg <invalid@invalid.invalid> wrote:>Phil Hobbs wrote: >> On 02/11/2013 04:03 PM, Joerg wrote: >>> 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? >>>> >>> >>> Quite a niche market, that probably gets expensive: >>> >>> http://c418683.r83.cf2.rackcdn.com/uploaded/BL_765670_e_ver2.pdf >>> >> I found one at Photonics West for $169, distributed by Ana Tek. (For >> Canadians with long memories, this isn't the power supply manufacturer >> from Vancouver.) >> >> http://www.anatekcorp.com/test%20equipment.htm . >> >> Doesn't seem to do gate leakage, though. The optimal combination might >> be one of these plus a bandaid box made of op amps, to increase the >> measured current by, say, 1E7 times to make the FET look more like a >> BJT. That would confuse its built-in functions completely, I expect. >> >> What I'm using now is a cast-aluminum Bud box with op amps in it, that >> generates a nice ramp for V_GS, has a knob for V_DS, and has TIAs for >> I_G and I_D. Works well but is a bit of a pain, and has no data acq. >> >> I could put something like that on the front of a Labjack (Joerg's >> fave). That would be a bit more dough, but I'll be needing to do a half >> dozen protos with data acquisition in the next few weeks anyway, so I >> can amortize the s/w labour over my gizmo and the client's work. (I >> hate charging clients for building libraries.) >> >> A standalone unit would be a lot nicer though. >> > >Hey, doesn't one of your kids want to get his hands dirty with some >software work? If you charge the client a lower rate for that work he >could still sock away a lot of money towards his first souped-up TransAm >with mag wheels and all that :-) > >If it's any comfort I'll have to design some radio circuitry soon and >build (yuck ...) several prototypes. Will use Labjacks again, mainly >because those come with a copy of a SCADA software to make life a bit >easier for SW-challenged guys like me. I just hope the garage ain't so >cold anymore once I get to do the boxes. But I don't envy you guys out >there right now, had a teleconference this morning and one guy is on >Long Island, snowed in.I was expecting a visit from a Pratt&Whitney guy. He lives near Hartford CT. His driveway is 400 feet long and maybe 40 feet wide. I calculated that he had roughly 400 tons of snow in the driveway. He rescheduled. -- 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 11, 20132013-02-11
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message news:362dnefOFo3kpoTMnZ2dnUVZ_oCdnZ2d@supernews.com...> 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 HobbsHello It looks like simple but working curve tracers are going unobtainium these days. It's either modular high-end systems for IC Fabs with the prices skyrocketing up the ISS or the homegrown fleabay stuff designed by people with no grasp of anything beyound current shunt resistors. There's a lot of hobby project schematics published in a hidden corners of the web that very nearly miss ending up on http://www.thedailywtf.com but only because the daily WTF does not know they exist (and does not care much about test equipment either). Also there are some boat anchors in unknown condition for sale, sometimes way overpriced because audiophools use the higher-voltage models in order to match tubes (whoever sells the QT2, listen, there's a new market for you). It looks like there's just no supply of affordable and usable curve tracers in the western corners of the world. There's a lot of Chinese curve tracers available, mostly analog ones, but the Chinese see no market for them in the west and don't even bother offering export versions with English user manuals or sometimes even front panel texts. Even worse, English-speaking search engines have difficulties finding anything, so most types are only findable with the proper "native" search terms. The "classic" instruments are really heavy (look up "QT2" for example, that thing is still produced) and haven't heared about a digital interface (or about the last 4 decades for that matter). There are newer versions like http://bayimg.com/KAjeIAAei (XJ4836). It's mains powered, but it at least has an USB interface. It's a rather sensitive small-signal tracer (by local standards), collector current down to 100nA/div, but no way for it to measure picoamps. Somewhat pricey too, given its specs, but at least it is standalone, PC-less and it is supposed to store settings and plots somewhere nonvolatile. If you search further, you may find the WQ4828 to WQ4830 type curve tracers too ( http://www.hzwqdz.com/ ), but they only go down to 200nA/div and their user interface will be a completely non-intuitive guesswork to anyone who does not have some Chinese friends to help translate it. They seem to be able to calculate more parameters however. Cheers Dimitrij Klingbeil
Reply by ●February 11, 20132013-02-11
tm wrote:> > This might be worth $24 to explore. Needs +/- 15 volts and a XY scope.$2 less in kit form. I have 25 new Integrated power designs SRW-65-4006 switching power supplies with +/= 15V outputs. http://034262c.netsolhost.com/wp-content/uploads/2011/06/SRW-65%20Specs.pdf and a small pile of used open frame Lambda, Power One etc linear supplies.> http://www.ebay.com/itm/140547987228?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649at lest they give you the schematic. :)
Reply by ●February 12, 20132013-02-12
On 02/11/2013 07:23 PM, John Larkin wrote:> On Mon, 11 Feb 2013 14:14:25 -0800, Joerg<invalid@invalid.invalid> > wrote: > >> Phil Hobbs wrote: >>> On 02/11/2013 04:03 PM, Joerg wrote: >>>> 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? >>>>> >>>> >>>> Quite a niche market, that probably gets expensive: >>>> >>>> http://c418683.r83.cf2.rackcdn.com/uploaded/BL_765670_e_ver2.pdf >>>> >>> I found one at Photonics West for $169, distributed by Ana Tek. (For >>> Canadians with long memories, this isn't the power supply manufacturer >>> from Vancouver.) >>> >>> http://www.anatekcorp.com/test%20equipment.htm . >>> >>> Doesn't seem to do gate leakage, though. The optimal combination might >>> be one of these plus a bandaid box made of op amps, to increase the >>> measured current by, say, 1E7 times to make the FET look more like a >>> BJT. That would confuse its built-in functions completely, I expect. >>> >>> What I'm using now is a cast-aluminum Bud box with op amps in it, that >>> generates a nice ramp for V_GS, has a knob for V_DS, and has TIAs for >>> I_G and I_D. Works well but is a bit of a pain, and has no data acq. >>> >>> I could put something like that on the front of a Labjack (Joerg's >>> fave). That would be a bit more dough, but I'll be needing to do a half >>> dozen protos with data acquisition in the next few weeks anyway, so I >>> can amortize the s/w labour over my gizmo and the client's work. (I >>> hate charging clients for building libraries.) >>> >>> A standalone unit would be a lot nicer though. >>> >> >> Hey, doesn't one of your kids want to get his hands dirty with some >> software work? If you charge the client a lower rate for that work he >> could still sock away a lot of money towards his first souped-up TransAm >> with mag wheels and all that :-) >> >> If it's any comfort I'll have to design some radio circuitry soon and >> build (yuck ...) several prototypes. Will use Labjacks again, mainly >> because those come with a copy of a SCADA software to make life a bit >> easier for SW-challenged guys like me. I just hope the garage ain't so >> cold anymore once I get to do the boxes. But I don't envy you guys out >> there right now, had a teleconference this morning and one guy is on >> Long Island, snowed in. > > I was expecting a visit from a Pratt&Whitney guy. He lives near > Hartford CT. His driveway is 400 feet long and maybe 40 feet wide. I > calculated that he had roughly 400 tons of snow in the driveway.And that he could probably afford a plough guy, or two. ;)> > He rescheduled. >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 12, 20132013-02-12
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 -- 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 12, 20132013-02-12
On 02/11/2013 07:27 PM, Jamie wrote:> 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 >> > A digital scope works well for that, it can be connected to the PC. > > You only need to create a test jig ramp signal that the scope can > trigger on. > > One could write the PC software and maybe even use a USB IO dongle to > control the test jig for various operations. >Sure, I know how to do it fully manually, and could build a proto of the front end in a day or so. What I want to avoid is spending a week getting all the features right. (Time is money and all that.) 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 12, 20132013-02-12
On Mon, 11 Feb 2013 14:29:37 -0800, mike wrote:> 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.The 7CT1 is perhaps mainly a qualitative device. The 576, which I use regularly, is capable of quite accurate measurements, used correctly. (Reminder to self, I must dig out the 2N7000 sub-threshold measurements I did in response to Jim T, and curve fit them)> > 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.That's what pulsed measurements are for. I regularly test devices at up to 200 amps, using a 176 pulsed high current fixture, without thermal problems.> > And the parasitics of the test fixture swamp device parasitics, unless > you use network analyzer fixturing.That applies to measurements generally. -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
