This paper describes the design and implementation of a dual channel oversampled A/D converter. The converter uses a cascaded 4th order sigma-delta modulator. Through the modification of modulator’s interstage gains

the modulator’ large signal overload problem is alleviatednd the maximum output signal to noise ratio is increased. A low noise current-steering logic is introduced to replace static CMOS for digital circuit design

which reduces the digital switching noise coupling in the A/D converter.The experimental chip is fabricated in 3μm CMOS technology. Test results show that

with a oversampling ratio of 64

a 91dB and 84.5dB dynamic range for two channels is achieved which uses current-steering logic and static CMOS respectively.