A 14mW 2.5MS/s 14bit Sigma-Delta Modulator Using Pseudo-Differential Split-Path Cascode Amplifiers

Switched-capacitor biased pseudo-differential split-path cascode amplifiers are proposed to achieve high power efficiency and small die area for a 14-bit 2.5MS/s DeltaSigma modulator. Sufficient power supply rejection is maintained through the biasing circuit. A novel signal and reference sampling network eliminates input common-mode voltages and relaxes op-amp linearity requirements, making it possible to use short channel length transistors for speed and power efficiency. A prototype chip is fabricated in a 0.25mum CMOS technology with a core area of 0.27mm
²
. Experimental results show that 84dB dynamic range is achieved with the 1.25MHz signal bandwidth when clocked at 120MHz. The power dissipation is 14mW at 2.5V including the on-chip voltage reference buffers