An 8-bit 200-MSample/s Pipelined ADC With Mixed-Mode Front-End S/H Circuit

This paper describes an 8-bit pipelined analog-to-digital converter (ADC) using a mixed-mode sample-and-hold (S/H) circuit at the front-end. The mixed-mode sampling technique reduces signal swings in pipelined ADCs while maintaining the signal-to-noise ratio. The reduction of signal swings relaxes the operational amplifier (opamp) gain, slew rate, bandwidth, and capacitor-matching requirements in pipelined ADCs. Due to the mixed-mode S/H technique, the single-stage opamps and small capacitor sizes can be used in this pipelined ADC, leading to a high speed and low-power consumption. Fabricated in a 0.18-mu m CMOS process, the 8-bit pipelined ADC consumes 22 mW with 1.8-V supply voltage. When sampling at 200 MSample/s, the prototype ADC achieves 54-dB spurious free dynamic range and 45-dB signal-to-noise and distortion ratio. The measured integral nonlinearity and differential nonlinearity are 0.34 LSB and 0.3 LSB, respectively.