An ultrasonic on-off keying/amplitude-shift keying demodulator using standard 0.18 mu m CMOS technology is proposed, intended for recovering the identification number of an implanted medical device transmitted from an external base station. The CMOS integrated ultrasonic demodulator consists of a low-noise amplifier, variable-gain-amplifiers, an offset cancellation circuit, an envelope detector circuit and a hysteresis comparator. Downlink data transmission of 50 kb/s data signals in the 1 MHz band is successfully demonstrated, the power consumption is about 184 mu W from a 1.5 V supply. The architecture is described, and the measurements performed confirm the theoretical result.