GΩ Resistor for AC-coupled Amplifier in Audio Application

Master thesis (2023)

Authors

J. WANG Electrical Engineering, Mathematics and Computer Science

Contributors

Q. Fan Microelectronics (mentor)
F.P. Widdershoven Bio-Electronics - EEMCS (graduation committee member)
Faculty
Electrical Engineering, Mathematics and Computer Science, Electrical Engineering, Mathematics and Computer Science
Copyright: © 2023 Junjie WANG
More Info
expand_more

Published Date

28-03-2023

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Electrical Engineering, Mathematics and Computer Science

Abstract

AC-coupled amplifiers (ACCA) offer lower noise than traditional resistor feedback
amplifiers, which benefits signal-to-noise ratio (SNR) for audio applications. Due to the
DC isolation of the capacitor, a feedback resistor is needed to set the virtual ground of
ACCA’s amplifier. However, an external feedback resistor raises system noise and
transforms the ACCA into a high-pass filter, impacting the audio bandwidth signal (20-
20kHz). A GΩ resistor can shift the cut-off frequency outside the audio bandwidth
while reducing noise. Various high-resistance resistor structures have been applied in
biomedical readout integrated circuits (ICs), such as sequence detection, ECG, and EEG
signal readout. However, the achieved signal-to-noise ratio and total harmonic
distortion (THD) are unsuitable for audio applications. This thesis discusses different
methods of making high-resistance resistors, such as duty-cycled resistors, switchedcapacitor resistors, and pseudo resistors, exploring their possibility in audio
applications. This work proposes an active current reducer structure with an
equivalent resistance of 200GΩ (± 20%) and an output RMS noise of 2.1μV for ACCA.
This circuit is built in the 180-nm BCD process achieving -106 dB to -116 dB THD and
96.7 dB SNR. Index Terms – audio amplifier, high-resistance resistors, duty-cycled resistor, switchedcapacitor resistor, pseudo resistor, active current reducers, total harmonic distortion
(THD).