一种新型高线性度MOS采样开关

A Novel Sampling Switch with Improved Linearity

提出了一种提高MOS采样开关线性度的新方法。通过采用电阻分压电路实现一个处于线性工作状态的“复制”MOS管,使其与采样MOS管具有相同的阈值电压。较之传统栅压自举开关,此新型MOS采样开关能够消除由于阈值电压随输入信号变化所产生的非线性。基于Char-tered 0.35μm标准CMOS工艺设计的新型采样开关,在输入信号为30 MHz正弦波,峰-峰值为1V,采样时钟频率为80 MHz时,无杂散动态范围达到了110 dB,较之自举采样开关提高了12 dB左右;同时,导通电阻的变化减小了90%。

A novel technique is proposed to improve the linearity of MOS sampling switch （SW） by generating a replica transistor with the same threshold voltage as the sampling transistor. The replica transistor is forced to oper ate in the triode region by means of resistive voltage divider. The effectiveness of this technique has been demonstrated by a prototype design of a sampling switch in 0. 35μm standard CMOS process, Sampled at 80 MS/s, the proposed switch in differential mode has a spurious free dynamic range （SFDR） of 110 dB for a 30 MHz and Vp-p = 1 V input signal, which is about 12 dB over the conventional switch. And the on-resistance variation is reduced by 90%.