A Simple and Efficient Charge Injection Error Compensation Structure for MOS Sampling Switches

Abstract

This paper introduces a new technique to design an analog MOS switch to be used in sampled-data circuits. In any sampled-data system, the accuracy of the sampling switch is a critical parameter to determine the overall performance of the system. To satisfy accuracy requirements of the switch, a novel technique to reduce channel charge injection error is proposed. The proposed switch has a very simple structure and it uses a small area of the chip. Also, it has a low on-resistance and its variation over the input signal range is acceptable. In order to evaluate the performance of the proposed switch, simulations are done in a 0.18[Formula: see text][Formula: see text]m standard CMOS technology. Simulation results show that the sampling errors produced by the channel charge injection is eliminated through a cancellation technique using an auxiliary transistor. The output error charge due to charge injection over a wide range of the input signal variation is very low (less than 1.45[Formula: see text]fC). Also, simulation results show that the proposed switch achieves signal-to-noise plus distortion ratio (SNDR) of 85.05[Formula: see text]dB, effective number of bits (ENOB) of 13.83, total harmonic distortion (THD) of [Formula: see text]87.23[Formula: see text]dB and spurious-free dynamic range (SFDR) of 88.14[Formula: see text]dB for a 1[Formula: see text]MHz sinusoidal input of 800[Formula: see text]mV peak-to-peak amplitude at 50[Formula: see text]MHz sampling rate with a 1.8[Formula: see text]V supply voltage.