This paper presents a 0.35 lm CMOS AM demodulator circuit. Design details, simulations and measurements results of the monolithic implementation of a highly accurate synchronous rectifier are shown. The cir- cuit implements an envelope detector with a ±1.5 V output swing on a 15 pF load. It dissipates 15 mW from a ±2.5 V voltage supply, and presents SNR = 81 dB measured at a THD =-40 dB for an input signal having 100% modulation index.