A CMOS Chopper Offset-Stabilized Opamp

摘要

In this paper, an offset-stabilized operational amplifier is described. The amplifier employs a chopper amplifier in a low frequency path to cancel the offset of a wide-bandwidth amplifier. A sample-and-hold circuit is used to reduce the chopper ripple, and the low frequency path is also offset-stabilized to further reduce the residual offset. The amplifier has less than 1.5 $mu{hbox{V}}$ offset at a 16-kHz chopper frequency, a unity gain frequency of 1.3 MHz with a 50-pF load, and draws 700 $mu{hbox {A}}$ from a 5-V supply. The amplifier was realized in a 0.7 $mu{hbox {m}}$ CMOS process, and has an effective chip area of 3.6 ${hbox {mm}}^{2}$.