Abstract: A novel,highly linear sampling switch suitable for low-voltage operation is proposed.This switch not only eliminates the nonlinearity introduced by gate-source voltage variation,but also reduces the nonlinearity resulting from threshold voltage variation,which has not been accomplished in earlier low-voltage sampling switches.This is achieved by adopting a replica transistor with the same threshold voltage as the sampling transistor.The effectiveness of this technique is demonstrated by a prototype design of a sampling switch in 0.35μm.The proposed sampling switch achieves a spurious free dynamic range of 111dB for a 0.2MHz,1.2Vp-p input signal,sampled at a rate of 2MS/s,about 18dB over the Bootstrapped switch.Also,the on-resistance variation is reduced by 90%.This method is especially useful for low-voltage,high resolution ADCs,which is a hot topic today.

Key words: sampling switch, nonlinearity, low-voltage, analog-to-digital converter, switched-capacitor circuits