Path: ...!weretis.net!feeder9.news.weretis.net!news.quux.org!eternal-september.org!feeder2.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Phil Hobbs Newsgroups: sci.electronics.design Subject: Re: Curve Tracers Date: Wed, 20 Nov 2024 22:26:05 -0000 (UTC) Organization: A noiseless patient Spider Lines: 78 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Wed, 20 Nov 2024 23:26:06 +0100 (CET) Injection-Info: dont-email.me; posting-host="1f79c4f5d5ebf1b78228a216717f9022"; logging-data="325521"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19H7EnF/Lpdu59+FYF7w+HB" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:y9aL9Vz9Yat28zqotS7iTIZ5Mnw= sha1:wI0HkPXtWxzXqH0c2E6kM6JhjTA= Bytes: 4228 john larkin wrote: > On Wed, 20 Nov 2024 18:00:34 -0000 (UTC), Cursitor Doom > wrote: > >> On Wed, 20 Nov 2024 07:40:08 -0800, john larkin wrote: >> >>> On Wed, 20 Nov 2024 11:32:32 -0000 (UTC), Cursitor Doom >>> wrote: >>> >>>> Gentlemen, >>>> >>>> Curve tracers reveal useful info about the dynamic characteristics of >>>> semiconductors and make designing for same much more predictable and >>>> dependable than relying on spice models and simulation alone. But >>>> they're typically rare beasts and expensive to come by and boat anchor >>>> varieties are seriously heavy and bulky. >>>> I think therefore that a curve tracer would make an excellent project, >>>> using the X&Y inputs of a scope as the display. Has anyone here >>>> attempted this? I'd be interested to know what the main challenges are >>>> likely to be. >>>> >>>> -CD >>> >>> I've considered it. It would be much more valuable if it traced >>> capacitances too. >> >> A VNA is best for that. I've been using my big HP one this afternoon to >> label some random bunches of caps and inductors whose values I couldn't >> read. Trouble is, there doesn't seem to be much agreement on what >> frequency to test these devices at. I've heard 100khz, 1Mhz, 10Mhz and >> 100Mhz mentioned from different sources. I'm pretty sure the 100Mhz >> testing is for RF specified devices only, though. From what I've seen, >> there's no reliable alternative to testing each batch for oneself, because >> (certainly with ancient NOS leaded (as in non-SMD) stock) you have no idea >> what frequency the factory tested them at and different manufacturers in >> different countries at different times used different methods! > > What I want is C-V curves. I guess a VNA can do that with a some bias > tees and various power supplies. > > > >> >>> The display should be on a computer and the data archived. >> >> For people such as yourself, certainly. For me as a hobbyist, a CRT is >> fine. > > You have to read the analog screen and write down numbers. Or take a > picture. > > >> >>> I often just set up a breadboard and test parts. Last week I blew out >>> some power mosfet gates. Some have internal zeners; this one doesn't. >> >> I can kill a MOSFET at 50' just by looking at it (certainly in winter). In >> fact I shock myself from all the static I build up and it ain't funny. >> Having dry skin is great for when I touch HV by accident (happens quite a >> lot) but the flip side is I accumulate and hold static charge like no one >> else I know. > > Some fets have protective gate zeners. They typically clamp at +-40 > volts. > > Here in San Francisco, we never get static zapped. High humidity. > I’ve done C(V) measurements with a Labjack and a Boonton 72A. Works great. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics