A current mode instrumentation amplifier based on the flipped voltage follower in 0.50 µm CMOS

This work presents the design of a current mode instrumentation amplifier (CMIA) based on the flipped voltage follower (FVF), used as a double current sense mechanism. Unlike current state of the art, the proposed CMIA senses the sourced and sank current of the voltage follower buffer inside the Op-Amp inputs. The FVF low-impedance input node allows to monitor the sink current provided by the low-impedance drain node of the active load in the voltage follower buffer. Proposed CMIA uses Split-Length compensated op-amps at the inputs, and Nulling-Resistor compensation technique is used at the output Op-Amp. The proposed CMIA is able to provide continuous programmable gains from 16 to 56 dB by adjusting R2/R1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_2/R_1$$\end{document} resistor ratios from 6.3 to 630 respectively. A gain-bandwidth product of 1.23 MHz and a common mode rejection ratio (CMRR) of 96 dB is obtained. A −3 dB CMRR cutoff frequency of 115 Hz is observed in all gain cases. An overall CMIA power consumption of 315.5 µW is measured; 95 µA at ±1.65 V. The proposed CMIA was simulated and fabricated using 0.50 µm ON-Semiconductor CMOS standard technology.