A low-voltage CMOS switch with a novel clock boosting scheme

There is a strong demand for an input switch in switched-capacitor circuits, covering rail-to-rail signal swing when low power-supply voltages are used. This brief proposes a novel clock-boosting scheme. The generated clock voltages of this new circuit are applied to a regular CMOS transmission gate to implement a simple and robust sampling switch when the supply voltages are very low. In this new approach, during the sampling phase, the gate-voltage of an nMOS switch is boosted up to V_dd+k·V_dd, and the gate voltage of a pMOS switch is lowered to V_gnd-k·V_dd, where k can be made programmable, and is usually smaller than 1. This allows sampling of the full signal swing, even when supply voltages are lower than |V_th,p|+V_th,n without applying extreme stress to the gate oxide of a transistor.