A Dual Synchronous Demodulator for Phase Sensitive Detection Applications

This paper presents an on-chip dual phase sensitive detector with an embedded multi tunable low-pass filter for impedance spectroscopy applications. Rectification process is achieved with a four switches demodulator, while DC components of target impedance are obtained by means of a first order fully differential low-pass filter. This Synchronous Demodulator (SD) system is programmable in gain (from 0 to 20 dB) with a 2-bit resolution and its cut-off frequency is tunable in a wide frequency range (from few Hz up to few hundreds of kHz). Phase recovery errors remain below 1.7° and are systematic, and hence easily compensated. Power consumption of SD is 36.1 p.W for a 1.8 V single supply implementation, thus making it suitable to be embedded in an integrated impedance measurement system.