A bandwidth-tunable bioamplifier with voltage-controlled symmetric pseudo-resistors

This paper describes a bioamplifier that employs a voltage-controlled-pseudo-resistor to achieve tunable bandwidth and wide operating voltage range for biomedical applications. The versatile pseudo-resistor employed provides ultra-high resistance for ac coupling to cancel the dc offset from electrode-tissue interface. The voltage-controlled-pseudo-resistor consists of serial-connected PMOS transistors working at the subthreshold region and an auto-tuning circuit that makes sure the constant (time-invariant) control-voltage of the pseudo-resistor. This bandwidth-tunable bioamplifier is designed in a 0.18-µm standard CMOS process, achieving a gain of 40.2dB with 10.35-µW power consumption. The designed chip was also used to develop the proof-of-concept prototype. An operation bandwidth of 9.5kHz, input-referred noise of 5.2 µ V rms from 6.3Hz to 9.5kHz and 5.54 µ V rms from 250Hz to 9.5kHz, and a tunable cutoff-frequency from 6.3-600Hz were demonstrated to prove our design.

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