A Distortion-Compensated Charge Transfer Amplifier for a 1.66-MHz Cyclic Pipeline ADC

Abstract

A distortion-compensated charge transfer amplifier (DCCTA) is proposed to improve the linearity constraints of the differential charge transfer amplifier (DCTA). The proposed DCCTA effectively reduces distortion at its output by source degeneration, cross coupling, and making the drain-to-source voltage of the amplifying transistor independent of the applied input signal. This DCCTA yields an effective number of bits of 9.26 bits, compared with 6.05 bits for the DCTA at 40 MHz while consuming only 13.5 μW from a 1.2-V source. A 1.66-MHz cyclic pipeline analog-to-digital converter employing this DCCTA as a residue amplifier was simulated using 90-nm CMOS process, resulting in a peak resolution of 9.21 bits, without being limited by the thermal noise.Index Terms-Charge transfer amplifier, cyclic pipeline analogto-digital converter (ADC), distortion compensation.