[sdiy] Transistor Matching (was moog high pass flter)

[Grant Richter]

The Moog app note says 2 millivolts, but by grading them into 1 millivolt
bins, you can easily match to 1 millivolt.

Silicon changes around 2 millivolts per degree C (variously quoted by
references any where between 1.8 and 2.7 mv/C)

So the Moog spec assumes a possible error of 1 degree C.

BTW, the exact value of the current source is not important, only that it be
repeatable.

> By the way, do you know how close transistors need to
> be? What is a good matching number to shoot for?
>