A 1-V 10-MHz clock-rate 13-bit CMOS /spl Delta//spl Sigma/ modulator using unity-gain-reset op amps

The problem of low-voltage operation of switched-capacitor circuits is discussed, and several solutions based on using unity-gain-reset of the opamps are proposed. Due to the feedback structure, the opamps do not need to be switched off during the reset phase of the operation, and hence can be clocked at a high rate. A low-voltage /spl Delta//spl Sigma/ modulator, incorporating pseudodifferential unity-gain-reset opamps, is described. A test chip, realized in a 0.35-/spl mu/m CMOS process and clocked at 10.24 MHz, provided a dynamic range of 80 dB and a signal-to-noise+distortion (SNDR) ratio of 78 dB for a 20-kHz signal bandwidth, and a dynamic range of 74 dB and SNDR of 70 dB for a 50-kHz bandwidth, with a 1-V supply voltage.