7. Mismatch Implications in Current-Mode Instrumentation Amplifiers

In the different CMIA topologies reported in previous chapters the final value of CMRR is determined by the matching between the used active elements. However, due to the stochastic nature of fabrication processes, the used active elements intended to be matched show different performances. In fact, high CMRR demands both a good circuit topology and a well matching between devices. Therefore, the designer should have good knowledge on both circuit design and mismatches. Owing to the critical role of mismatches in the performance of CMIAs, this chapter reports a brief study on the effect of mismatches in CMIA design. In the first section, a short analysis on the mismatch in CMOS technology is given. Then, the effect of mismatches in different structures of CMIAs is discussed. Later, some effective techniques helpful in reducing mismatches are reviewed. In the last section, a current input CMIA topology with robust performance against mismatches is shown.