Transistor curve tracing in this century - Page 1
Forum section: electronics / testgear

author: mcovington
author_rank: Regular Contributor
timestamp: December 15, 2019, 09:20:47 pm
content: I have my trusty Tek 575, which helps hold my house down when it's windy, but...I would have thought that in this day and age, a transistor curve tracer would be a device that connects to a PC by USB, using the PC to do all the curve plotting.I don't see those. I still see curve tracers that connect to oscilloscopes, or look like oscilloscopes, and are very expensive.What am I missing? Why does the kind of curve tracer that I imagine not actually exist? Should I get started designing one?

author: Grandchuck
author_rank: Super Contributor
timestamp: December 15, 2019, 09:39:22 pm
content: I have one of these and it works very well:https://www.peakelec.co.uk/resources/dca75.html

author: Gyro
author_rank: Super Contributor
timestamp: December 15, 2019, 09:44:41 pm
content: +1 Great little tool (especially if you can get someone to 3D print their bench stand design for you).

author: Someone
author_rank: Super Contributor
timestamp: December 15, 2019, 10:05:07 pm
content: Quote from: mcovington on December 15, 2019, 09:20:47 pmIts now called a dual channel SMU, they usually come with example curve tracing software to get you started.

author: Cerebus
author_rank: Super Contributor
timestamp: December 15, 2019, 10:10:56 pm
content: The phrase you're looking for, in current equipment, is "Semiconductor Device Parameter Analyzer" or something similar.Which will lead you to something like theKeysight B1500A Semiconductor Device Parameter Analyzer/Semiconductor Characterization System MainframeIf Sir needs to ask "how much?", Sir can't afford it.The thing that separates something like that from something like the baby Peak analyser is range. The B1500A specs cover current source/measurement ranges of 0.1 fA - 1A, and 0.5uV - 200V voltage source/measure, with a 200 MS/s sampling rate for investigating pulsed parameters. The Peak goes up to 10V and 15.5 mA and doesn't specify a minimum current - the highest zener voltage you can characterise with it is 9V.The difficulty in designing a useful curve tracer equivalent that would connect to as PC via USB is choosing the ranges to cover. If you want to cover only small signal devices (i.e. omitting what we might characterise as 'power' devices') you probably want a pair of USB computer controlled source/measure units that can handle say 50V and 500mA and have mV and sub-uA measurement resolution respectively - which implies something on the order of 20 bit resolution which is non-trivial to achieve in practice.Oh, and ideally you want to be able to sourceandsink current, which means your SMU design would need to operate in at least 2 quadrants.

author: David Hess
author_rank: Super Contributor
timestamp: December 15, 2019, 10:47:42 pm
content: I just have a Tektronix 7CT1N but it sure has been handy.Syscomp Design makes a USB curve tracer among other USB instruments:https://www.syscompdesign.com/product/ctr-201/

author: Shock
author_rank: Super Contributor
timestamp: December 16, 2019, 08:36:14 am
content: There are simple audio card curve tracers as well, look hard enough and probably free ones. I think the advantage of the old Tek models is the large power supplies, plus testing two devices at once and having various test fittings on those specific models. If you want a cheap component tester the Chinese AVR ones are dirt cheap and you can also buy the octopus kits as well.One of the personal distinctions for me is I don't want to necessarily test just low voltages devices. The Tek 576 seems to be one of the more desirable vintage models and covers low voltage, 1nA per division and comes with a 1.5kV anode supply that powers up to 220W or 20A. For this reason you can test small devices right up to large devices. It's easy to make DIY test fittings as well as it uses banana style sockets and if you DIY an external heater supply it makes an ideal tube tester.Tektronix has an old "Measurment Concepts" book which is a good introduction for anyone who hasn't seen it, that along with the manuals of course.I have an old Tek 576 in the restore queue so one day (clenched fist).

author: 001
author_rank: Super Contributor
timestamp: December 16, 2019, 11:00:28 am
content: Quote from: Shock on December 16, 2019, 08:36:14 amCan You link me?

author: fcb
author_rank: Super Contributor
timestamp: December 16, 2019, 01:40:08 pm
content: +1 for the Peak Electornics DCA75. However it will only go to 10-12V and a few mA.

author: Johnny10
author_rank: Frequent Contributor
timestamp: December 16, 2019, 02:13:16 pm
content: I haven't followed it properly but Dos4ever uTracer tube curve tracer has a Lab Note for turning it into transistor curve tracer.Check out Ronald's site, lots of great information in the Lab Notebook.The uTracer was my first DIY electronics project!

author: voltsandjolts
author_rank: Unknown
timestamp: December 16, 2019, 03:08:23 pm
content: Dual channel sig gen maybe:https://translate.google.com/translate?sl=nl&tl=en&js=y&prev=_t&hl=nl&ie=UTF-8&u=https%3A%2F%2Fwww.circuitsonline.net%2Fforum%2Fview%2F141079&edit-text=&act=url

author: exe
author_rank: Unknown
timestamp: December 16, 2019, 03:19:38 pm
content: I use analog discovery + a few resistors + external PSU. Before that I used siggen and an oscilloscope. An SMU would be cool, but they are very pricey. The cheapest one I saw was $1k.

author: Zucca
author_rank: Unknown
timestamp: December 16, 2019, 03:24:06 pm
content: Quote from: exe on December 16, 2019, 03:19:38 pmThis.

author: all_repair
author_rank: Frequent Contributor
timestamp: December 16, 2019, 03:29:48 pm
content: Wait 6 month or a year, a Chinese ham already selling a kit version for a curve tracer +/-28V 500mA version with PC that has preloaded curve of some of the device from their datasheet to be compared with what being captured. I already have a locky_z curve tracer, so waiting for the next iteration of this kit version with higher voltage and current range.

author: 10101
author_rank: Contributor
timestamp: December 16, 2019, 04:20:01 pm
content: There's always the diy route xD

author: DaJMasta
author_rank: Super Contributor
timestamp: December 16, 2019, 05:05:00 pm
content: You can get older mainframe based SMUs at somewhat more reasonable prices, and while they are not frequent, something like a U2722A can go under the radar for most SMU purchasers and go for a bit less (not the same name/model recognition as the Keithleys, for example) while being compact and having good performance.If you have a bench supply and a load (resistors and a meter or electronic), you can get all the same data, it's just a matter of the software (or graph paper) that actually generates the curve.Alternatively, you can get or build a relatively simple device that uses a sig gen and a scope to give you a curve tracer, there have been a number of projects described in other sections of the forum, but I think they're available as kits/fully assembled on ebay and others, and there are lots of designs that can be used.

author: tmbinc
author_rank: Frequent Contributor
timestamp: December 16, 2019, 05:32:10 pm
content: Was about to say - I have a U2722A and I'm reasonably happy with it. Not that I have used it as much as I had planned to but I have a number of "shelved" projects (that I'll un-shelve, one day!) that need this.Obligatory board images.

author: Shock
author_rank: Super Contributor
timestamp: December 16, 2019, 07:39:56 pm
content: Quote from: 001 on December 16, 2019, 11:00:28 amhttp://w140.com/tekwiki/wiki/Concepts_SeriesSemiconductor Device Measurementshttp://w140.com/tekwiki/images/a/a0/062-1009-00.pdfIf you are interested in the Tek 576, similar to the HP journals they also cover products in the magazines.http://w140.com/tekwiki/wiki/Tektronix_MagazinesThe Tek 576 was introduced in Vol. 1 No. 1, Feb 1969 of Tekscope.http://w140.com/tekwiki/images/7/76/Tekscope_1969_V1_N1_Feb_1969.pdfAs a side note these with inflation would be $14K instruments today.

author: TimFox
author_rank: Super Contributor
timestamp: December 16, 2019, 08:27:29 pm
content: Quote from: David Hess on December 15, 2019, 10:47:42 pmThe Syscomp unit looks interesting, but it has been discontinued..They advise me that a replacement is expected in 2020.Do you know what the price was before discontuance?

author: fcb
author_rank: Super Contributor
timestamp: December 16, 2019, 10:04:36 pm
content: Here's a project I am finishing at the moment.It is a small dual channel SMU we call "SMUSB" - basically a low-cost 2 channel SMU. Video was shot in April 2019 and I've just switched it from private to public.This describes the various prototypes we went through with the project.https://youtu.be/KkDIATgGuxI

author: David Hess
author_rank: Super Contributor
timestamp: December 17, 2019, 12:47:40 am
content: Quote from: TimFox on December 16, 2019, 08:27:29 pmIt was like $400 so not exactly cheap.

author: rodpp
author_rank: Frequent Contributor
timestamp: December 17, 2019, 05:06:37 pm
content: Quote from: David Hess on December 17, 2019, 12:47:40 amIf its test voltage/current range were similar to the Tektronix boat anchors, that price would be great. But definitely, it is not.

author: jonpaul
author_rank: Super Contributor
timestamp: December 19, 2019, 02:01:34 pm
content: Hi there, I have had TEK 577, somewhat smaller than 576 but similar.My lab has a 576 in perfect condition with all test fixtures and printed manual. Very useful and essential for power electronics work. The 7CT1N and similaire TM 500 CT plug-in are rare and hard to use.I Suggest to Look at Ham Radio Fleas.To build one, Search DIY articles in 1960s....1980s consumer electronics magazines like Popular Electronics, Radio Electronics and ham radio magazines like QST and 73.Just the ramblings of an old retired EEJon

author: RoGeorge
author_rank: Super Contributor
timestamp: December 19, 2019, 03:08:50 pm
content: My question is why would one need curve tracer, other than for didactic purposes?I needed one only once, while I was trying to find out if an optical sensor from a very old punch cards reader is in fact a photodiode or a phototransistor. Ended up improvising a curve tracer with a simple coil (transformer) that was laying around, a signal generator and the humble Rigol DS1054Z in XY mode. Conclusions were not so obvious, but the device looked more like a phototransistor on the curve tracer. The decisive tests, thought was while looking at the chip's die under microscope, it looked like a disc circled by a ring, so a phototransistor layout.What would be the nowadays typical use for curve tracer?

author: Johnny10
author_rank: Frequent Contributor
timestamp: December 19, 2019, 04:17:54 pm
content: Because they are just so damn cool !

author: CDaniel
author_rank: Frequent Contributor
timestamp: December 19, 2019, 04:25:21 pm
content: You could match some transistors with that ...

author: David Hess
author_rank: Super Contributor
timestamp: December 19, 2019, 05:49:00 pm
content: Quote from: RoGeorge on December 19, 2019, 03:08:50 pmSome transistor failure modes are not revealed by breakdown, leakage, and hfe tests.

author: Someone
author_rank: Super Contributor
timestamp: December 19, 2019, 10:18:56 pm
content: Quote from: David Hess on December 19, 2019, 05:49:00 pmMore generally, some semiconductor parameters are not mentioned in data sheets.

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 19, 2019, 10:29:58 pm
content: Given the quantity of counterfeit semiconductors floating around, you can use one to verify you have what you thought you bought.+1 on David Hess's comment; I've had situations where the only way to identify a bad component was to put it on a curve tracer.

author: aqibi2000
author_rank: Regular Contributor
timestamp: December 19, 2019, 10:42:50 pm
content: Quote from: Cerebus on December 15, 2019, 10:10:56 pm

author: mcovington
author_rank: Regular Contributor
timestamp: December 20, 2019, 12:23:18 am
content: It sounds like I should keep my Tek 575 for the rest of my life because there will never be anything else like it.I'll sell it when it needs a major repair that I don't want to get involved in, or when someone makes me an offer I can't refuse. (Local pickup in Athens, Georgia, only.)The last time I used it, just the other day, was to characterize a pair of transistors tied together at the bases and collectors to work like back-to-back Zeners -- something Dave introduced on one of his videos.http://www.covingtoninnovations.com/michael/blog/1909/index.html#x190920http://www.covingtoninnovations.com/michael/blog/1912/index.html#x191202

author: all_repair
author_rank: Frequent Contributor
timestamp: December 20, 2019, 01:53:18 am
content: Quote from: David Hess on December 19, 2019, 05:49:00 pmCan you elaborate more? I would like to learn what are they.

author: David Hess
author_rank: Super Contributor
timestamp: December 20, 2019, 03:39:56 am
content: Quote from: all_repair on December 20, 2019, 01:53:18 amTo give an example, I found a bad 2N3565 in a Tektronix DC505 frequency counter. The puzzling thing was that the transistor appeared good but the curve tracer revealed that it had a very soft knee when entering saturation and an Early voltage (collector resistance) which degraded at high collector voltage. Further testing revealed that about half of the 2N3565s in the DC505 displayed this behavior to some extent; so I replaced them all.The poor saturation could be explained by high emitter resistance like from bond wire failure. That combined with degraded Early voltage at high collector voltage probably means something to someone more familiar with bipolar transistor fabrication.

author: Berni
author_rank: Super Contributor
timestamp: December 20, 2019, 07:30:22 am
content: I have a HP 4145B (Semiconductor parameter analyzer) that fits somewhere in between the Tek 576 and the modern stuff.Its still old enough to carry the HP logo but modern enough to be fully digital, including its green vector CRT.Its basically a 4 channel SMU that can go up to 100V or up to 100mA (Not simutaniusly) and provides 50 femtoamp resolution so you can look at the leakage curves of semiconductors. You give a list of things to measure and it will plot pretty curves on the screen or export them to a 3.5in floppy disk. You can also read the channels live if you want a electrometer.Occasionally you can find one of these for a good price, but its easier to find a HP 4141B for a good price. That thing is basically the same as the 4145B but includes no user interface on the front panel so you need to do all of your interaction trough the GPIB port. A lot of these ware used in semiconductor fabs filling racks of production testing equipment, so all they needed was GPIB.EDIT: Oh and beware that all of these HP SMUs mentioned above have 4 or 5 triax connectors on the back. If you ever bought a triax cable you know the financial horror of it, if you haven't, then look up at how much those cost.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 20, 2019, 12:42:42 pm
content: Hmmm, I have a Tek 577 to poke at one day.It has at least one burnt tantalum inside, so a recap is in order.I got no jigs for it, bit the test box thingo still has the clear plastic cover attached, so it's not all bad.I also made an ebay kit curve tracer that works well, but no USB.I wonder how hard it would be to attach some A/D converters to the scope output to feed the data into a PC?

author: Berni
author_rank: Super Contributor
timestamp: December 20, 2019, 01:02:12 pm
content: Quote from: TERRA Operative on December 20, 2019, 12:42:42 pmIf you have anywhere near a modern scope you can just write a script to download a X Y plot trace over USB, LAN, GPIB... etcBy the way the real value of a proper curve tracer is having enough dynamic range to produce a logarithmic scale plot of the DUT. This makes it possible to capture detail in a single plot of both the area where the device conducts as well as the leakage in the area it is not supposed to be conducting, along with it also the area in between how it transitions between conducting and not conducting.But as a quick fault finding device the classical DIY 50/60Hz transformer and XY scope based curve tracer is the way to go because of how fast it does the measurement(50/60 times a second) and you are not concerned about accuracy, you just want to see if the thing you are poking is acting like a diode. It also has a bonus that capacitance and inductance shows up as a circle.

author: 001
author_rank: Super Contributor
timestamp: December 20, 2019, 05:45:44 pm
content: Quote from: Berni on December 20, 2019, 01:02:12 pmThat do You mean?

author: David Hess
author_rank: Super Contributor
timestamp: December 20, 2019, 09:12:16 pm
content: Quote from: Berni on December 20, 2019, 01:02:12 pmI usually use a function generator and power supply to hack something together.

author: TheBay
author_rank: Unknown
timestamp: December 20, 2019, 09:14:37 pm
content: Quote from: Berni on December 20, 2019, 01:02:12 pmThis is why I love Hameg CRO's, as they nearly all seem to have that built in, invaluable bit of test gear for quick fault finding of a board or some components, they are worth buying just for that feature even if the scope side of it doesn't get used. The Huntron Tracker is also useful and can be found quite cheap.Had a load of "Fake" BLW96/76's turn up in work because of some bean counter upstairs, I needed to check them quickly and the DCA75 was invaluable for that, great tool for the money, especially connected to the PC.

author: duak
author_rank: Super Contributor
timestamp: December 20, 2019, 09:17:58 pm
content: Occasionally I want to test out or even characterize a component at various voltages and currents. What I think I could use is a variable voltage supply with both voltage and current imits and not have an output capacitor. The current limit would be variable from 1 uA to say 1 A. The current sense would be at least as good and would have a fast logarithmic display. A curve tracer is more specialized but can sort of be set to do some of what I want. I'd use it to test or match transistors or other simple semiconductors. I've got more than a few house numbered devices I'd like to use for something and this gizmo would help.Another Tekster, Dennis Feucht, has a series of articles on Two Port Analyzers, a generic term for curve cracers starting at:https://www.planetanalog.com/build-your-own-curve-tracer-part-1-introduction/David Hess points out that transistors can have anomalous characteristic rather than be fully bad and sometimes it's at an odd combinations of voltage and current or whatnot. One example is that when I was building my own 'scope in the 70's, I used some ECG replacement bipolar transistors for the vertical deflection amp outputs. They were probably CRT cathode drivers and so were rated for a few hundred volts and had good ft. The display had a strange distortion that I couldn't quite figure out. I didn't have a scope so I had to rig up something to check the transfer function. It turned out that one of the devices had a strange positive feedback characteristic that made it act like a weak SCR at certain collector-emitter voltages.

author: David Hess
author_rank: Super Contributor
timestamp: December 20, 2019, 09:52:45 pm
content: Quote from: TheBay on December 20, 2019, 09:14:37 pmTektronix has some old application notes where they discuss various ways to use the sweep output on an analog oscilloscope to do simple curve tracing.