A high-speed fully differential current switch

Abstract

A high-speed differential-mode current switch is presented. The clock-feedthrough effect is reduced by swing-reduced drivers (SRD's) and neutralized by dummy transistors. With the use of SRD's, the switching transistors never operate in the triode region, which provides good matching of capacitance between the switching transistors and dummy transistors. The SRD's also reduce the possible large current spikes on the outputs of the current switch. Analysis shows this current switch is ideal for high-speed current-mode signal processing. A continuous-time switched-current /spl Sigma//spl Delta/ modulator using these current switches has been implemented in a 2 /spl mu/m CMOS process and achieved a 59 dB dynamic range with a 50 MHz clock.