Design of a low noise single-ended sensor interface amplifier for bio-potential applications

Document Type : Original Article


1 Military technical College

2 Electronic Engineering Department, Military Technical College


This paper discusses a low-noise read-out amplifier circuit for a
biomedical sensor interface. The amplifier has two amplification stages
with a Miller compensation capacitor that offers high gain with a large
output swing. For power efficiency, all transistors are operated in a
sub-threshold regime that makes the design suitable for implantable
and portable medical devices. The proposed design works at the heart
of bio-medical sensor interface circuits. It offersan amplification for
different bio-potential signals such as electroencephalogram (EEG),
electrocardiogram (ECG), and electromyogram (EMG) according to
its bandwidth (BW). Furthermore, a small signal model analysis of the
proposed amplifier is presented. A chopping technique is also proposed
to reduce the sensor offset voltage and the flicker noise generated from
sensor interface circuits. The proposed amplifier design achieves a gain
and a BW of 62.16 dB and 506 Hz respectively. The input commonmode
range (ICMR) varies from 0.3 V to 0.8 V with a phase margin
(PM) of 62.57◦ at VCM equals 0.3 V and 66.8◦ at VCM of 0.8 V. The
circuit is designed in 130 nm CMOS technology and consumes a power
of 0.4 μW from 1 V supply. Also, the chopping technique reduces inputreferred
voltage noise from 38.445 μV/sqrt(Hz) to 3.06 μV/sqrt(Hz)
within a frequency range from 0.01Hz to 500Hz.


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