Digital Control of Analog Level

In many audio product designs, the level of an analog signal must be varied by a digital controller. This paper discusses several approaches to the design of circuits which accomplish this task. Stepped attentuators, such as multiplying digital-to-analog converters (MDACs) and switched resistor networks, as well as digitally controlled voltage-controlled amplifiers (VCAs) are discussed. The paper presents several criteria with which to evaluate different circuit implementations, and points out some of the merits and liabilities of each approach.