Fully Differential AC-Coupling Networks: A Comparative Study

Óscar Casas

doi:10.1109/TIM.2008.927200

2009-01-01

PRE

Óscar Casas *

Enrique Mario Spinelli

R. Pallás-Areny

DOI：10.1109/TIM.2008.927200

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摘要

En 中文

Fully differential ac amplifiers can easily be designed by placing an ac-coupling network in front of a fully differential dc amplifier. Such a network, however, must have a high common-mode rejection ratio (CMRR) to keep the overall CMRR high. In principle, passive ac-coupling networks that include no grounded components have an infinite CMRR, but they must provide a path for input bias currents. This paper analyzes how component tolerances limit the CMRR and affect the transient response of three different ac-coupling networks. To evaluate these networks in real conditions, the common-mode input impedance and bias currents of the ensuing differential amplifier are considered. Experimental results confirm the theoretical predictions.

Keyword:

AC measurements

differential amplifiers

differential circuits

passive filters