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    Item type:Publication,
    A 38.4 nW, 1.2 V, 250-Hz, 2nd-Order gm - C LPF With Degenerative SCP Transconductors Achieving 800-mVPP Input Range and 82.1- μVrms IRN for ECG Acquisition
    (2025-01-01)
    Thanapitak, Surachoke
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    Pawarangkoon, Prajuab
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    Surakampontorn, Wanlop
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    Ahmad, Rafidah
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    Abdullah Zawawi, Ruhaifi
    In this brief, a 2{^{\text {nd} -order gm - C lowpass filter with a practical input linear range of 400mV P dedicated to ECG signal acquisition is proposed. This filter employs a degenerative source-coupled-pair circuit as a gm cell. It enhances the linear input range by a factor of × 4 compared with the source follower filter. Additionally, to mitigate the effect of current source mismatch, a dynamic element matching technique is applied. By doing so, HD2 is suppressed more than 1.5 dB over the entire passband frequency. This proposed filter is implemented in a 0.18 μ m CMOS process. It offers a 250-Hz bandwidth with input-referred noise and a dynamic range of 82.1 μ Vrms and 67.34 dB, respectively. The power consumption of 38.4 nW is achieved with a 1.2 V supply. Compared with other recent nano-power filters, the proposed filter provides the highest linear input range with competitive Figure-of-Merit to the top-tier designs. It is therefore beneficial to the practical implementation of a low-power ECG acquisition system.
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    Item type:Publication,
    Voltage-mode biquad filter using three lt1228s with independent and electronic control of center frequency and quality factor
    (2023-01-01)
    Wai, May Phu Pwint
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    ; ; ;
    Chanapromma, Chaiyan
    In this paper, we describe a voltage-mode (VM) biquad universal filter with one input and four outputs that can be tuned electronically. The filter proposed here is composed of three LT1228 commercial integrated circuits (ICs), seven resistors and two grounded capacitors. The proposed versatile biquad filter simultaneously provides four filtering functions: An inverting low-pass filter (LP), an inverting high-pass filter (HP), a non-inverting bandpass filter (BP), and an inverting notch filter (BR) without changing its topology. Employing two grounded capacitors minimizes the influence of parasitic resistances and capacitances on the proposed circuit's performance. Also, the output voltage nodes of the HP and BR functions have low output impedances. This means that these two filtering functions don't need voltage buffers to connect to other voltage-mode topologies. The center frequency (ω<inf>0</inf>) of the presented filter is electronically controlled and does not influence the quality factor (Q). In addition, they can also be tuned linearly without affecting each other. PSPICE software was used to analyze the modelling results, while a laboratory experiment was performed using LT1228 commercial ICs.
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    Item type:Publication,
    New realization of single CFCTA-based voltage-mode multifunction filter
    (2018-06-08)
    Chanapromma, Chaiyan
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    ;
    The realization of voltage-mode second-order multifunction filter using current follower cascaded transconductance amplifier (CFCTA) is presented in this contribution. The proposed circuit has three voltage input nodes and a single voltage output node. Its natural frequency and quality factor are electronically adjusted. Also, the control of the quality factor is done without affecting the natural frequency. Five filtering functions, low-pass filter (LPF), high-pass filter (HPF), band-pass filter (BPF), band-reject filter (BRF) and all-pass filter (APF), are obtained with the same circuit topology. The selection of each filter response meets the requirement of no active and passive element matching conditions. The PSpice simulation results of all five filtering functions along are included to verify the theoretical analysis.