Integrated signal processing circuits for silicon microphones

This paper presents the design of signal processing circuits for silicon microphones which consist of interface circuit, anti-aliasing low pass filter and A/D converter. These circuits have been designed using Cadence/Spectre® simulator. The overall circuits use single 3.3V power supply both of analog part and digital part in 0.8µm CMOS technology. An interface circuit part includes a buffer circuit and an amplifier circuit. This stage has signal gain of circuit equal to 20dB. In an anti-aliasing low pass filter circuit part, the cutoff frequency of this circuit is equal to 22 kHz. The A/D converter part contains a 4th order switched-capacitor single loop feedback low pass delta sigma modulator. This modulator uses an input signal with bandwidth of 20 kHz and clock frequency of 2.4 MHz. Therefore, the modulator obtains an oversampling of 60 and SNR of 91dB, respectively. The output signal of modulator is 1 bit digital signal which is obtained up to 14 bit resolution. The total power consumption of proposed system is 20mW.