PCM telephony: reduced architecture for a D/A converter and filter combination

Large dynamic range and high power-supply rejection ratio (PSRR) are achieved in a pulse-code-modulation (PCM) decoder by using differential circuit techniques and by reducing the number of operational amplifiers on the interpolation filter to four (including the output buffer). This reduction is achieved by: (1) exploiting the sin x/x distortion and using a simple integrating configuration in the digital-to-analog converter; and (2) properly manipulating the signal flowgraph of the filter.<
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