A 1V-70dB THD Digital Controlled Audio AGC

Abstract

This paper presents a 1V -70dB THD audio Automatic Gain Control (AGC) circuits. The proposed AGC is based on feedback topologies and the gain is digital controlled. A π-type resistors network is used in the Programmable Gain Amplifier (PGA) as the passive feedback device to realize gain linearity in decibels and increase the gain accuracy. The hysteresis comparator eliminate the chattering effects when the output signal of Peak Detector changes rapidly around the threshold. The design is implemented in 0.18μm CMOS and occupies an active area of 0.41mm2. The power consumption of AGC is about 0.17mW at 1V supply voltage. The gain of PGA in the AGC loop ranges from 0dB to 40dB in 2dB step with gain error not more than 0.2dB. The integrated noise in the audio range (20 Hz~20 kHz) is 2.28μVRMS when the gain is set at 40dB. The total harmonic distortion (THD) is below -70dB over the audio frequencies at 0.4-Vpp differential output.