High Performance Column Level ADC for CMOS Imager using Switched Capacitor Technique

Abstract: An integrating type analog to digital converter is commonly used to achieve a high resolution. In this work 12-bit Dual slope ADC is developed which is an integrating type ADC. To integrate the input signal it requires one integrator made up of one resistance in feed forward path and one feedback capacitance with opamp circuit. Switched capacitor based integrator is alternative technique to realize the integrating function. In this design resistance in feed forward is replaced with two switches and one capacitor. This technique requires non overlapping clock. One of the advantages of this technique is area minimization. This technique is easily compatible with technology. This dual slope column level ADC minimizes the conversion time. Two stage opamp is designed which has gain of 78.22 dB. This column level dual slope ADC is implemented using 180nm standard CMOS technology.

Keywords: ADC, CIS, CMOS, OPAMP.