A Differential Difference Amplifier with Dynamic Resistive Degeneration for MEMS microphones

摘要

A Fully Balanced Differential Difference Amplifier (FB-DDA) with Dynamic Resistive Degeneration (DRD) is presented. Thanks to this technique, the tradeoff between noise and distortion proper of classic FB-DDA is overtaken, by means of a “Smooth Transition Controlling Circuit” that guarantees low noise performances for small input levels and low distortion performances for high input levels. The circuit has been adopted as the main buffering element in a direct readout circuit for MEMS analog microphones realized in a 0.13um CMOS process performing 112dB Dynamic Range and a maximum THD of about 1.6% with a -2dBV Input Signal.