Analytical expressions for harmonic distortion at low frequencies due to device mismatch in CMOS current mirrors

One of the origins of harmonic distortion in current mirrors is the inevitable mismatch between the mirror transistors. In this brief, we examine both single current mirrors and complementary class-AB current mirrors, and develop analytical expressions for the mismatch-induced harmonic distortion. The expressions are verified through simulations and are used for a discussion of the impact of mismatch on harmonic distortion properties of CMOS current mirrors. The distortion model is combined with well-known statistical models for the device mismatch in order to establish a relation between geometrical parameters, distortion, and production yield. It is found that distortion levels somewhat below 1% can be attained by carefully matching the mirror transistors, but ultra-low distortion is not achievable,