A Low-Noise Area-Efficient Current Feedback Instrumentation Amplifier
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A Low-Noise Area-Efficient Current Feedback Instrumentation Amplifier R. Sanjay1 · B. Venkataramani2 · S. Kumaravel1 · V. Senthil Rajan2 · K. Hari Kishore2 Received: 19 November 2019 / Revised: 11 August 2020 / Accepted: 14 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The low-power current feedback instrumentation amplifier (CFIA) circuits using local feedback configuration are reported in the literature for biomedical applications. However, they have limitations such as low gain, higher area, and higher noise due to the need for higher source degeneration resistors (in tens to hundreds of k), and higher minimum achievable bandwidth (in tens of kHz). In this paper, a low-power, low-noise CFIA using closed-loop configuration is proposed to overcome these limitations. It uses a folded cascode operational transconductance amplifier with a lower value of source degeneration resistor (in the order of few k) in the input stage to reduce the noise without compromising the loop gain. As the bandwidth of the proposed CFIA is defined as unity-gain bandwidth of the CFIA’s loop gain, it can be reduced below 10 kHz without increasing area. The proposed CFIA is designed and implemented in a 0.35 µm CMOS process for a current of 9.6 µA with a supply voltage of 3 V, and its performance is evaluated through simulation. It has a gain of 34 dB, total input-referred noise of 3 µVrms , and a noise efficiency factor of 3.81. It achieves a bandwidth of 8.8 kHz using a load capacitor which is more than four times smaller than that of local CFIA. It provides an input signal swing of 16 mVpp at THD of 1% and the CMRR of 118 dB. Keywords Current feedback instrumentation amplifier · Low-noise · Low-power · Area-efficient · Common-mode rejection ratio (CMRR) · Noise efficiency factor
1 Introduction Due to the developments in CMOS technology, wearable devices become alternative to the traditional bulky biomedical devices. They offer low weight and cost. They are used for measuring biopotential signals such as electrocardiogram (ECG), electroen-
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R. Sanjay [email protected]
Extended author information available on the last page of the article
Circuits, Systems, and Signal Processing
cephalogram (EEG), and electromyogram (EMG) [7]. The amplitude and frequency ranges of the biopotential signals are 10 µV–10 mV and 0–10 kHz, respectively [14]. For EMG and neural spikes, the signal lies below 10 kHz [13, 26]. The ECG/EEG signals and local field potentials (LFPs) lie below a few hundreds of Hz [18, 26]. Since the wearable device has multiple channels, the power and noise requirements of each channel should be low [18]. The analog front end (AFE) of each channel consists of an instrumentation amplifier (IA), programmable gain amplifier, and low pass filter (LPF). A single analog-to-digital converter (ADC) is multiplexed among the different channels [10, 23]. The crucial block of the AFE is the IA. Additional to the precise power and noise requirements, the IA should also have high gain, high CMR
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