Analysis of non-idealities in parallel-summation logarithmic amplifiers

Abstract

CMOS logarithmic amplifiers based on piecewise linear approximation have been usually analyzed and designed by assuming ideal conditions. This paper discusses non-ideal factors in the used components, which play a key role in the performance of high-accuracy logarithmic amplifiers for sensing applications, and shows that the use of simplified mathematical models may lead to wrong conclusions. A gain-mismatch compensation method that enables wide dynamic range and low-power operation is also outlined.