With the rapid advances in communication technologies, the PCM approaches have been widely used to transmit many signals through a single channel due to its high performance. In the IC implementation of the PCM encoder/decoder the CMOS process is most advantageous. In this paper we assume a 2-μm CMOS process. The transmit and smoothing filters are also included in this CODEC chip where μ-255 companding law is employed on the input side of the ADC within the encoder and the charge-redistribution technique is used for an A/D conversion. Accordingly, the D/A conversion is of an expanding type to restore the original dynamic range of the companded input. Great efforts were made to increase the system performance as a whole by enhancing performances of the individual components involved.
