Dynamic input offset auto-compensation of continuously working opamp

The operational amplifier offset compensation is usually realized as a switched circuit working in two main phases. During the first phase the amplifier compensates its own offset and in the second one it is processing signal as an application needs. The compensation itself is then made either in analog [1] or digital [2] mode. Unfortunately this kind of solution cannot be used in case an application demands continuous signal processing. This problem can be solved by topology which uses two amplifiers. The first of them (auxiliary amplifier) works again in two phases. During the first phase it compensates its own input offset while during the second phase it continuously measures and controls offset of the main opamp. There exists more techniques allowing the continuous offset compensation of the main (or both) opamps by extra input. The presented solution was designed and manufactured in CMOS07 technology and allows designer to simply use even already designed Miller-OTA opamps with minimal adaption.