A CMOS Linear Preamplifier Design for Electret Microphones

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 9dB. Simulated peak signal-to-noise and distortion ratio (SNDR) is 62 dB at 100mVpp with 2pF switching capacitor load at 2.56 MHz. The preamplifier operates under 1.8V supply voltage and the total current consumption is 190 mu A. It has been designed for a 0.18 mu m MOS technology.