A novel differential synchronous demodulator for AC signals

We describe a new analog differential synchronous demodulator for AC signals where: (i) the signal is synchronously demodulated using the floating capacitor technique after being amplified, if necessary, by a low-gain AC amplifier with differential input and differential output, thus yielding a very high CMRR; and (ii) the differential-to-single ended signal conversion is performed after demodulation, that is, on a low-frequency signal that can be amplified by low-cost, high-performance circuits. We prevent the possible signal-to-noise ratio degradation because of synchronous sampling by using bandpass differential filters