Current-mode quadrature ring oscillator for bioimpedance applications

A tunable frequency current-mode quadrature ring oscillator for bioimpedance spectroscopy applications is presented. It consists of four cross-coupled differential delay cells implemented using log domain circuits. The oscillation frequency can be fine-tuned using the bias current of the delay cells...

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Bibliographic Details
Main Authors: German-Sallo, Z., Groza, R., Onet, R., Neag, M.
Format: Conference Proceeding
Language:English
Subjects:
Bioimpedance
Capacitors
current control
Current measurement
current mode ring oscillators
Delays
externally linear internally nonlinear circuits
MOSFET
Ring oscillators
Spectroscopy
subthreshold
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Summary:A tunable frequency current-mode quadrature ring oscillator for bioimpedance spectroscopy applications is presented. It consists of four cross-coupled differential delay cells implemented using log domain circuits. The oscillation frequency can be fine-tuned using the bias current of the delay cells and coarse tuned by modifying the capacitors of the delay cells. The ring oscillator output current can be used for bioimpedance measurements as a current stimulus via a current buffer. Two quadrature output currents are converted using current-input comparators to in-phase and quadrature square voltages needed for demodulation on the bioimpedance readout side. The ring oscillator was implemented in a standard 180nm CMOS technology using MOS transistors operating in weak inversion. The oscillation frequency can be modified from 7.27kHz to 15.13MHz, while consuming from 1.05mA to 1.23mA from a 2V supply voltage.
ISSN:2377-0678
DOI:10.1109/CAS52836.2021.9604153