On-chip in-situ measurements of Vth and AC gain of differential pair transistors

In-situ DC measurements of individual transistors in a differential pair of an analog amplifier derive threshold voltage, V_th, of 1.0-V transistors in a 90-nm CMOS technology. On-chip continuous time waveform monitoring is used to evaluate AC response of the same amplifier. The distribution of AC gain versus V_th of transistors within amplifiers is captured. The degradation of common-mode rejection property is observed for an amplifier with intentionally introduced mismatches to the pair of transistors.