Owen Duffy wrote:
Operation of a diode detector in the square law region isn't out of the
question, but it takes some serious gain to drive a meter. There are some
good chopper stabilised op amps out there that have uV offset levels and
single supply rail and input to below the negative rail eg LTC1050.

If the diode is DC-biased and the bias subtracted out
during calibration, doesn't that improve the low power
accuracy considerably?
--
73, Cecil http://www.w5dxp.com