A Switched-Capacitor Variable Gain Amplifier for CCD Image Sensor Interface System

摘要

A new topology for a switched-capacitor variablerngain amplifier (SC-VGA) is proposed and implementedrnin an analog-digital interface system for CCD imagernsensor. The SC-VGA exploits a positive feedback whichrnleads to simpler circuit implementation, lower powerrnconsumption and reduced kT/C noise, compared to thernconventional one. The gain, controlled by 8-bit digitalrnsignal, varies from 0 dB to 24 dB with 0.094-dB step.rnThe measured gain of the SC-VGA shows monotonicityrnover the whole range of the gain (DNL < 1). Fabricatedrnin 0.25-um CMOS process with MIM capacitors, thernVGA occupies 0.25 mm~2 and dissipates 5 mW at 8 MHzrnwith a supply voltage of 2.8 V.