A CMOS linear preamplifier design for electret microphones

Abstract

A gm-opamp-RC configured CMOS linear preamplifier for electret microphone is presented in this paper. The transconductance amplifier (gm-cell), as a V/I convertor at the input stage of the preamplifier, adopts a negative feedback loop at its input pair to enhance the linearity of the output current. Feedback loop improves the SFDR of the preamplifier by 9 dB. Simulated peak signal-to-noise and distortion ratio (SNDR) is 62 dB at 100 mVpp with 2 pF switching capacitor load at 2.56 MHz. The preamplifier operates under 1.8 V supply voltage and the total current consumption is 190 muA. It has been designed for a 0.18 mum CMOS technology.