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CMOS Design, Simulation and Physical Design of a Two Channel Demodulator

Elumalai R, K.M.Vanitha, ElavaarKazhali

In this paper, we present a two channel direct demodulator design for differential signals. The twochannel demodulator accepts two independent input signals in a differential mode and demodulates to provide a filtered DC output. Based on analog multiplexer (AM) select pin, one channel is selected out of 2 channels for the differential signal (v1,v2) processing. Demodulator section consists of precision full wave rectifier (PR), 2ndorder Butterworth low pass filter (AF), and summing & difference amplifiers (SA & DA).The Filtered outputs are added, subtracted & amplified to get -(v1+v2) & (v2-v1) outputs respectively which are of bipolarities. This finds applications in processing signals from differential transformers. The mentioned method of demodulation is much superior to that of synchronous demodulation on parameters of noise performance, phase error, additional clock, components count and accuracy.