Re: gEDA-user: powermeter power supply update

[DJ Delorie <dj@xxxxxxxxxxx>]

> 4.5 watts? That must be one hell of a flashlight.

It's a big 6v rechargable one.  The flashlight doesn't work, but the
bulb does.

> > One of these days I'm going to make a digitally-controlled load.  It's
> > just a monster FET with some control circuitry, right?
> 
> Basically, yes. But in order to dial in resistances you must find two 
> that are nearly identical (pairs are rare in the power class)

I saw an appnote about one FET that had a different temperature
coefficient, so could be used paired (for heavier loads), because if
one overheats it *reduced* its conductivity - they ended up balancing.
But I suspect that's not what you're talking about - you're talking
about a current mirror, yes?

> and servo it with an opamp.

I knew that part.

> Or just command currents, then it's down to one big FET.

One FET, one current sense resistor, and an opamp, plus however you
derive the control setting for it.


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