Path: ...!eternal-september.org!feeder2.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: john larkin Newsgroups: sci.electronics.design Subject: Re: Curve Tracers Date: Thu, 21 Nov 2024 15:43:21 -0800 Organization: A noiseless patient Spider Lines: 134 Message-ID: <09hvjjta6p3t9ffe2ji2j30hnautcvdmqa@4ax.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Date: Fri, 22 Nov 2024 00:40:57 +0100 (CET) Injection-Info: dont-email.me; posting-host="05fd96ecd694b13a3a46499bb19a3509"; logging-data="908274"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+az0tUx+O872sGBkZzR8t8" User-Agent: ForteAgent/8.00.32.1272 Cancel-Lock: sha1:JOxFcNJHnjyZZa6PcqBUO+Y4WtY= Bytes: 6875 On Thu, 21 Nov 2024 23:35:13 -0000 (UTC), Cursitor Doom wrote: >On Thu, 21 Nov 2024 08:03:00 -0800, john larkin wrote: > >> On Thu, 21 Nov 2024 12:02:28 -0000 (UTC), Cursitor Doom >> wrote: >> >>>On Wed, 20 Nov 2024 16:37:39 -0800, john larkin wrote: >>> >>>> On Thu, 21 Nov 2024 00:00:10 -0000 (UTC), Cursitor Doom >>>> wrote: >>>> >>>>>On Wed, 20 Nov 2024 12:27:04 -0800, 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. >>>>> >>>>>If you only want C/V curves, what's wrong with a plain 'scope and a >>>>>pulse generator? >>>> >>>> How would you do that? >>> >>>Ah! Well, I obviously mis-read your earlier statement. My bad, soz. >>> >>>>>>>> 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. >>>>> >>>>>It would only be a (slight) issue if I needed to share an image with a >>>>>third party. Aside from that, there's nothing I couldn't live with. >>>>>You're obviously requiring more than that, though. >>>>> >>>>>>>> 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. >>>>> >>>>>So you never need to wear a wrist/earth strap? That's a big plus. I >>>>>find them *so* restrictive and irritating when they (invariably) catch >>>>>on something. >>>>> >>>>>>>> Most mosfets drain avalanche, but the voltage is never specified, >>>>>>>> in fact deliberately hidden. I have to measure that. A good curve >>>>>>>> tracer should measure that too. >>>>>>>> >>>>>>>> Currents should go down to picoamps. >>>>>>>> >>>>>>>> The fact that there aren't many curve tracers for sale suggests a >>>>>>>> small market. >>>>>>> >>>>>>>But a market, though small perhaps, there must be. >>>>>> >>>>>> Sure. It would be a fun project. >>>>> >>>>>And with thanks to Trump's tariffs, you might even make a few buxx out >>>>>of it, too. >>>> >>>> Is there going to be tariffs on USB capacitance-measuring curve >>>> tracers? >>> >>>Not specifically, but I imagine Trump will want tariffs on Chinese >>>imports in general, which should give some breathing space profit-wise >>>to US manufacturers. >>>I have to say I do admire Trump's job creation ideas, which should >>>produce solid results, as opposed to old Joe's approach of destroying US >>>jobs, seemingly on purpose. I say old Joe's approach, but what I really >>>mean is the approach of the Globalists who tell him and his ilk what to >>>do. >> >> We should stop paying the Chinese for the shipping costs of cheap junk, >> for starters. > >The US does that too?? Wow. I thought that was just a European thing. The Chinese are a "disadvantaged country" per the International Postal Union. They will ship a cheap ebay thing here for free. It would cost me a bundle to ship it back.