MOS DIGITALLY CONTROLLED ANALOG ATTENUATOR FOR VOICE-BAND SIGNALS

This paper describes the design of an analog attenuator integrated circuit having loss settings that can be determined by remote digital control. The circuit uses a weighted MOS capacitor array to effect losses of 0-16.5 dB in steps of 0.1 dB. Each loss setting is accurate to ±0.02 dB. Two approaches to the circuit realization are described: a CMOS version that includes a digital memory to permit retention of loss settings for a few hours, thereby bridging brief power failures, and a more compact NMOS version that contains all the analog components on a single chip. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.