A Low-Voltage Sampling Switch with Improved Linearity

A novel high linear sampling switch suitable for low-voltage operation is proposed. It not only eliminates the nonlinearity introduced by the gate-source voltage variation, but also reduces the nonlinearity resulting from the threshold voltage variation which is not solved in the earlier low-voltage sampling switch. This is achieved by adopting a replica transistor which has the same threshold voltage as the sampling transistor. The effectiveness of this technique has been demonstrated by a prototype design of a sampling switch in 0.35 mum. Simulations show that the sampling switch has a more constant on-conductance and a significant higher SFDR. This method is especially useful for low-voltage, high resolution ADCs, which is one of the hot topics nowadays