Zero-drift operational amplifiers

This article considers the design and implementation of four different zero-drift operational amplifiers with 50 nm technology CMOS and compares their characteristics. The aim is minimizing input offset voltage and flicker noise. Offset voltage is unavoidable in operational amplifiers, because no two transistors can be identical. A small difference in their dimensions (length or width) gives rise to this undesirable effect, the value of offset voltage in common operational amplifiers is less than 10 mV. In this article, two major techniques of dynamic offset cancellation, chopping and auto-zeroing, are considered. The operational amplifier with chopping shows the best result among the four amplifiers.