RE: N Ch MOSFET & Zenner Diode Test Adapter

shabaz — Wed, 12 Nov 2014 15:27:11 GMT

I think one of the best ways to learn about different semiconductor devices is to do exactly this, play around with multimeters and adjustable levels or signals and observe the effect. A while back I tried a tunnel diode (something I'd always wanted to experiment with, but never obtained one until a few years back). It was a lot of fun, and I learned a lot.

I too wanted to design something similar as you have done, but with voltage and current sources (i.e. like a curve tracer) but I abandoned it because it grew way too complicated : (

Really nice design - it looks great!! I need to get some of those test points you're using - I keep forgetting to add them to the shopping cart.

RE: N Ch MOSFET & Zenner Diode Test Adapter

D_Hersey — Wed, 12 Nov 2014 14:45:32 GMT

Hi, John

Many bulb filaments don't exhibit much resistance when they are cold. Electrons flow through them initially like Aaron Rogers' passes through the Bear's D during a first half. As an aside, uPs with power Qs can ramp bulbs up by modulating duty-cycle. This usually gives the bulb a longer lifetime by avoiding thermal shock. Using this technique on the filaments of thermionic devices is similarly useful. When they (incandescent bulbs) are intended for illumination they are often coupled with inrush surge limiters. You might make your load partly resistive, or a current source. I presume you are using a fuse. We should have choice in our top load to accommodate Q's of different sizes and shapes. Try EBAY with the terms 'selector switch ceramic.'

Modulating supply power to achieve AM of your gate signal doesn't give me a 'downtown feel.' It works, but has a lower limit as you state. Why not use an (RRIO) op amp (maybe w/ push-pull buffer stage on the output) and potentiometer and passives after your oscillator to allow more adjustment range? Vgs-th can be quite low, nowadays. Version 3 should feature a uP, IMHO.

Good to see you re-using stuff! Good-on-ya, Greenie!