Discrete-Time Circuit Design

Analog filters, ADCs and DACs that only process sampled analog signals can operate as discrete-time (DT) circuits controlled by the sampling clock. The DT circuits prove to be easy to simulate at behavioral level, as they only employ half-clock and 1-clock delays. Hence their functioning as linear systems can be modeled using Z-transforms, the same transforms used to analyze digital filters. These circuits often show advantages at transistor level, taking advantage of the higher switching speeds available in the deep sub-micron MOS transistors. Disadvantages of using discrete-time circuits include high transient currents on the supply lines and long transistor-level simulation times.