Of course, there are much better ways to match transistors as you have correctly pointed out. However, without access to a curve tracer or without building a test circuit for detailed measurements, the simple measurements of beta that these testers can give will at least get you in the ballpark.Good videos - a bit of a refresher for me, but I did learn a new trick for testing those mosfet's by charging the gate and discharging through my finger (why didn't I think of that?) Every failed FET I've ever seen has shown a failure mode of a short from drain to source though too.
I do have a question...
To properly match transistors don't you need to see the transistor curves on a curve tracer and try to select transistors with similar curves? Most beta testers only test at a single current (usually about 1mA base current). I've noticed that gain can vary wildly with base current. I assume this is mostly due to the early effects in the transistor. I don't know that measuring a single point beta really matches a pair of transistors. Not in my experience anyway trying to make current mirrors. Care to comment?
Love your vids and I would love to hang out and pick your brain on Electronics ...
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by Jake Hertz
by Jake Hertz