A current-mode, 1.5 V, 30 Ms/s CMOS sample-and-hold circuit with 9-to 10-bit accuracy

Abstract

The possibility of realizing a 1.5 V and 30 Ms/s video-rate CMOS sample-and-hold circuit with 9- to 10-bit accuracy has been studied. The current-mode circuit technique has been adopted to enable the sample-and-hold circuit operate in 1.5 V of supply voltage. The sample-and-hold uses current mirrors whose node voltages are completely fixed in order to avoid the influence of the gm and the output conductance variation of a transistor when signal current changes. Sample switches are placed differentially in between current mirror transistors, which eliminates the undesirable clock feed-through from analog switches. The designed circuit was actually fabricated by using standard CMOS 0.6 μm process and its characteristic was evaluated. The signal-to-noise ratio of 57 dB and 54 dB at a clock speed of 20 MHz and 30 MHz, respectively, were measured from the 1.5 V supply voltage with the power dissipation of 2.3 mW.