Next Article in Journal
Lightweight Thermal Compensation Technique for MEMS Capacitive Accelerometer Oriented to Quasi-Static Measurements
Next Article in Special Issue
Low-Power Wireless Sensor Network Using Fine-Grain Control of Sensor Module Power Mode
Previous Article in Journal
Fast and Sensitive Bacteria Detection by Boronic Acid Modified Fluorescent Dendrimer
Previous Article in Special Issue
A Low-Power 12-Bit 20 MS/s Asynchronously Controlled SAR ADC for WAVE ITS Sensor Based Applications
Article

Analysis and Reduction of Nonlinear Distortion in AC-Coupled CMOS Neural Amplifiers with Tunable Cutoff Frequencies

Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059 Kraków, Poland
*
Author to whom correspondence should be addressed.
Academic Editors: Francesc Serra-Graells, Michele Dei, Kyoungrok Cho and Federico Alimenti
Sensors 2021, 21(9), 3116; https://doi.org/10.3390/s21093116
Received: 28 February 2021 / Revised: 16 April 2021 / Accepted: 21 April 2021 / Published: 30 April 2021
(This article belongs to the Special Issue Integrated Circuits and Systems for Smart Sensory Applications)
Integrated CMOS neural amplifiers are key elements of modern large-scale neuroelectronic interfaces. The neural amplifiers are routinely AC-coupled to electrodes to remove the DC voltage. The large resistances required for the AC coupling circuit are usually realized using MOSFETs that are nonlinear. Specifically, designs with tunable cutoff frequency of the input high‑pass filter may suffer from excessive nonlinearity, since the gate-source voltages of the transistors forming the pseudoresistors vary following the signal being amplified. Consequently, the nonlinear distortion in such circuits may be high for signal frequencies close to the cutoff frequency of the input filter. Here we propose a simple modification of the architecture of a tunable AC-coupled amplifier, in which the bias voltages Vgs of the transistors forming the pseudoresistor are kept constant independently of the signal levels, what results in significantly improved linearity. Based on numerical simulations of the proposed circuit designed in 180 nm technology we analyze the Total Harmonic Distortion levels as a function of signal frequency and amplitude. We also investigate the impact of basic amplifier parameters—gain, cutoff frequency of the AC coupling circuit, and silicon area—on the distortion and noise performance. The post-layout simulations of the complete test ASIC show that the distortion is very significantly reduced at frequencies near the cutoff frequency, when compared to the commonly used circuits. The THD values are below 1.17% for signal frequencies 1 Hz–10 kHz and signal amplitudes up to 10 mV peak-to-peak. The preamplifier area is only 0.0046 mm2 and the noise is 8.3 µVrms in the 1 Hz–10 kHz range. To our knowledge this is the first report on a CMOS neural amplifier with systematic characterization of THD across complete range of frequencies and amplitudes of neuronal signals recorded by extracellular electrodes. View Full-Text
Keywords: CMOS neural amplifier; AC coupling; pseudoresistor; nonlinear distortion; area-efficient design CMOS neural amplifier; AC coupling; pseudoresistor; nonlinear distortion; area-efficient design
Show Figures

Figure 1

MDPI and ACS Style

Trzpil-Jurgielewicz, B.; Dąbrowski, W.; Hottowy, P. Analysis and Reduction of Nonlinear Distortion in AC-Coupled CMOS Neural Amplifiers with Tunable Cutoff Frequencies. Sensors 2021, 21, 3116. https://doi.org/10.3390/s21093116

AMA Style

Trzpil-Jurgielewicz B, Dąbrowski W, Hottowy P. Analysis and Reduction of Nonlinear Distortion in AC-Coupled CMOS Neural Amplifiers with Tunable Cutoff Frequencies. Sensors. 2021; 21(9):3116. https://doi.org/10.3390/s21093116

Chicago/Turabian Style

Trzpil-Jurgielewicz, Beata, Władysław Dąbrowski, and Paweł Hottowy. 2021. "Analysis and Reduction of Nonlinear Distortion in AC-Coupled CMOS Neural Amplifiers with Tunable Cutoff Frequencies" Sensors 21, no. 9: 3116. https://doi.org/10.3390/s21093116

Find Other Styles
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop