VP64 Voltage-Programmable Gain Amplifier

Voltage-Programmable Gain Amplifier Voltage-controlled amps (VCAs) are everywhere.  Their primary use is extending the dynamic range of A/D converters, so that we can preserve the dynamic range of our measurements,  They mostly work great at high gain; however, there's something their makers don't tell you straight out: they're horribly noisy at low gain, so our SNR gets trashed. The reason is that the variable-gain element they use is the transconductance of a BJT differential pair, which can handle only about ±50 mV, maximum. If the output range is ±10 V, the fixed-gain part runs at a gain of about 200. Thus in order to make a gain of 2, say, the typical VCA attenuates the signal by a factor of 100, and then multiplies it by 200. Mathematically this is fine, but in electronics, a lot of noise gets added in the process, costing typically 30 dB of SNR at higher signal levels.  Our VP64 Voltage-Programmable Gain Amplifier provides gains from 0.125× - 64× (-18 dB - 36 dB), with almost n