Re: Curve Tracer

On Tue, 04 Feb 2025 23:03:34 +0000, Cursitor Doom <cd@notformail.com>
wrote:

On Tue, 04 Feb 2025 10:19:40 -0800, john larkin <jl@glen--canyon.com>
wrote:
>

On Tue, 04 Feb 2025 16:51:22 +0000, Cursitor Doom <cd@notformail.com>
wrote:
>

Gentlemen,
>
I've decided a nice project would be to build a curve tracer which
would (because I'm a vintage nut) use a CRT display of an
oscilloscope. From time to time I have these Big Ideas and it could
conceivably become the latest in a long line of my unfinished
projects.
>
Which curves would be essential to include for a decent, functional
design? I know what the obvious ones are; just wondering if there are
any more obscure ones which would be advantageous to plot. Finally,
are there any additions one could make to a classic curve tracer's
functionality which were omitted from the early designs (modulation
feature at 1Mhz,100Mhz or whatever) for example?
>
CD.

>
I'd like to see pulsed avalanche behavior of mosfets, preferably to
destruction.
>
C-V curves would be great too.
>
Stuff that's not on the data sheet.
>
The thing about an analog CRT scope is that it isn't quantitative and
forgets instantly. A digital scope would fix that. A curve tracer
should be able to trigger the scope and do short single-shot events.

>
DSOs have their own disadvantages for this sort of thing.
These people make this little thing with a CT function, but it needs a
computer screen and is only capable of applying up to 10V! The stupid
fucks have only used a single AAA battery for its power source. Can
you believe that? I suspect there'll be a revised model along in due
course which has a far better voltage range.
>
https://www.peakelec.co.uk/acatalog/dca75-dca-pro-semiconductor-analyser.html

Given a digital scope, most measurements can be done in a millisecond
or less, so a curve tracer can have some tiny power supplies and a few
big caps.

People don't use bipolar transistors much any more, so one could
emphasize tracing mosfets and GaN fets and SiC parts.

When I need to characterize a part, I hack up a setup with power
supplies and pulse generators and stuff.  We have a Tek scope with 4
isolated channels, which is handy snooping drain currents and such.