GΩ Resistor for AC-coupled Amplifier in Audio Application

GΩ Resistor for AC-coupled Amplifier in Audio Application

WANG, Junjie (TU Delft Electrical Engineering, Mathematics and Computer Science)

Fan, Q. (mentor)
Widdershoven, F.P. (graduation committee)

Delft University of Technology

Electrical Engineering

2023-03-28

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). 

High resistance resistors
Pseudo resistor
Audio Amplifiers

http://resolver.tudelft.nl/uuid:07ad594f-1d13-4b78-9fed-92606ddf7cb1

Student theses

master thesis

© 2023 Junjie WANG