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A new scheme for an A-law PCM encoder is presented. It is based on charge redistribution in a single array of 11 binary weighted capacitors. Use is made of a double polysilicon n-MOS process which is compatible with advanced integrated filter techniques such as CCDs or active LSI filters with ratioed capacitors. No operational amplifier is needed, enabling low power dissipation and standard supply voltages (+5, -5, +12 V). It also features an improved multiple access comparator with a sensitivity better than 2 mV without charge degradation from feedthrough effects.
Date of Publication: Jun 1978