AN AUTOMATIC OFFSET COMPENSATION SCHEME WITH PING-PONG CONTROL FOR CMOS OPERATIONAL-AMPLIFIERS

An automatic offset compensation scheme for CMOS operational amplifier s is presented. Offset is reduced by digitally adjusting the bias volt age of a programmable current mirror which is used as the load of the differential input stage. A 100% operating duty cycle is obtained by u sing a ping-pong structure. The offset compensation scheme is inherent ly time and temperature stable since the offset compensation is period ically performed with the ping-pong control. The proposed circuit has been fabricated using a 1.0 mum n well CMOS process. The measured offs et voltages of the test circuits are less than 400 muV in magnitude.