Low Noise AC Amplifier with Programmable Gain and Bandwidth

Two LTC6910 programmable gain amplifiers can be combined to provide independent gain and bandwidth control using two 3 bit digital words. The Gain Control PGA simply varies the circuit gain from 1 to 100. The Bandwidth Control PGA puts signal gain inside the feedback loop of the amplifier. As this gain is increased the effective value of feedback resistor R2 is decreased. This pushes out the upper low pass corner frequency of the ac amplifier.