A Sub-1V Fourth-Order Bandpass Delta-Sigma Modulator

A sub-1V fourth-order bandpass delta-sigma modulator is presented in this paper. Using the switched opamp technique enables the modulator to operate at only 0.8 V supply voltage without using voltage multipliers or bootstrapping switches. A two-path structure is applied to relax the settling requirement. Implemented in a 0.25-μm one-poly, five-metal standard CMOS process, the prototype modulator exhibits a signal-to-noise-plus-distortion ratio (SNDR) of 58.2 db and a dynamic range (DR) of 64 db in a 60 KHz signal bandwidth centered at 1.25 MHz while consuming 2.5 mW and occupying an active area of 2.11 mm ².