Design of low power, programmable low-G m OTAs and G m -C filters for biomedical applications
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Design of low power, programmable low-Gm OTAs and Gm-C filters for biomedical applications V. Senthil Rajan1 • B. Venkataramani1 Received: 4 August 2020 / Revised: 19 October 2020 / Accepted: 3 November 2020 Ó Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this paper, two programmable operational transconductance amplifiers (POTAs)—one using bulk driven attenuator (BDA) and another using programmable current mirror (PCM) are proposed in order to achieve low-Gm and high dynamic range. These OTAs are denoted as BDA-POTA and PCM-OTA respectively and are realized using composite transistors operated in the subthreshold region. The pseudo resistor is used for achieving programmability in the former and for improving the linearity and dynamic range in the latter. The proposed OTAs and two 4th order programmable Butterworth low pass filters (LPF) are designed and implemented in CMOS 180 nm technology with a supply voltage of 0.9 V. Their performances are evaluated through post-layout simulations and are found to be superior compared to those of POTAs reported in the literature for biomedical applications. The power consumption, transconductance, dynamic range and inputreferred noise of BDA-POTA and PCM-OTA are [25.2 nW, (7.89–15.61 nS), (77.54–74.89 dB), (39.86–51.19 lVrms)] and [72.81 nW, (5.49–174.5 nS), (91.20–84.39 dB), (17.19–34.92 lVrms)] respectively. The power dissipation and cut off frequency range of the LPF using BDA-POTA and PCM-OTA are [197.8 nW, (30–100 Hz)] and [209.8 nW, (16–971 Hz)] respectively. The latter achieves 13.6 times wider programmability with only 5% increase in power dissipation. The proposed LPFs have better FOM compared to those reported in the literature. Keywords Programmable low-Gm OTA Bulk driven attenuator Low voltage Low power Programmable Butterworth low pass filter
1 Introduction The monitoring and processing of biomedical signals such as filtering and removal of out-of-band noise are the primary functions in portable, implantable and wearable biomedical devices such as cochlear implants, breathing detectors, cardiac-pacemakers, heart rate detectors, etc. These devices have stringent performance requirements such as lower cutoff frequencies, lower area and lower power dissipation in order to decrease the weight and to enhance the life of battery [1]. The advancements in CMOS technologies have made the realization of the devices meeting these requirements feasible and propel & V. Senthil Rajan [email protected] 1
Analog and Digital IC Design Laboratory, Department of Electronics and Communication Engineering, National Institute of Technology, Tiruchirappalli, India
further advancements in these devices [2–4]. Continuoustime filters are used for filtering and eliminating out-ofband noise encountered in biomedical signals (such as ECG, EMG and EEG) lying in the frequency range of 10 mHz to 10 kHz [5]. These filters require low cutoff frequencies. If these filters are programmable, they can be used to process different biomedical signals by va
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