[sdiy] mixer

[jh.]

> Also, tricks used for error cancellation in precision circuits, like
having a
> resistor in series with the + input that is the same as the equivalent
resistance
> seen by the - input (eg, Rf || Rin) is actually detrimental, because there
is no
> phase cancellation of noise between the + and - inputs - everything adds
as RMS
> (the square root of the sum of the squares of all the individual noise
sources).

This "trick" is for reducing offset voltage comming from input bias current,
not for noise reduction. I think it even *adds* noise, so better bypass it
with a capacitor.

JH.