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    Current-mode variable current gain first-order allpass filter employing CFTAs
    (2013-01-01)
    Iamarejin, Anirut
    ;
    Maneewan, Suwat
    ;
    ;
    In this study, a current-mode first order allpass filter using current follower transconductance amplifiers (CFTAs) is proposed. The features of the circuit are that: the pole frequency, phase response and current gain can be electronically controlled via the input bias current: the circuit description is very simple, consisting of 2 CFTAs, 1 resistor and 1 grounded capacitor, without any component matching requirements. Consequently, the proposed circuit is very appropriate to further develop into an integrated circuit. Low input and high output impedances of the proposed configuration enable the circuit to be cascaded in current-mode without additional current buffers. The PSpice simulation results are depicted. The given results agree well with the theoretical anticipation.
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    Electronically tunable voltage-mode SIMO OTA-C universal biquad filter
    (2011-12-01) ; ;
    Dejhan, Kobchai
    This paper presents a new voltage-mode biquad filter with single-input multiple-output (SIMO) based on single-ended operational transconductance amplifiers (OTAs) and grounded capacitors. The proposed filter can provide lowpass, bandpass, highpass, bandstop and allpass voltage characteristics. The natural frequency can also be tuned electronically by adjusting the transconductance values of OTAs. The filter still enjoys no requirement with the component choice conditions and no requirement with the inverting-type input signal to realize specific filtering functions, high input impedance, and low active and passive sensitivities. PSPICE simulation results are provided to demonstrate the theoretical analysis. © 2011 IEEE.
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    A new quadrature sinusoidal oscillator for telecommunication system using VDDDAs
    A CMOS voltage differencing differential difference amplifiers (VDDDAs) based voltage-mode quadrature sinusoidal oscillator is proposed. The proposed oscillator is based on the two integrator loop configuration with amplifier wherein the frequency of oscillation (FO) is tuned by the time constant of two integrator and the condition of oscillation (CO) is tuned by gain of amplifier. It is constructed from two VDDDAs, two resistors, and two grounded capacitors. With this structure, it is attractive to develop in monolithic chip. The tuning of frequency of oscillation can be electronically done without affecting the condition of oscillation. Also, the condition of oscillation can be adjusted by external resistor without affecting to frequency of oscillation. The simulation results have been demonstrated and discussed using parameters of 0.18um TSMC CMOS technology and +0.9V power supply voltages.
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    Electronically tunable voltage-mode universal filter with single-input five-output using simple OTAs
    (2013-08-01) ; ;
    Dejhan, Kobchai
    This article presents a new electronically tunable voltage-mode universal biquadratic filter with single-input five-output using simple operational transconductance amplifiers (OTAs) and grounded capacitors. The proposed configuration provides low-pass, band-pass, high-pass, band-stop and all-pass voltage responses at a high-impedance input terminal that enables easy cascading in voltage-mode. The natural frequency and the quality factor can be set orthogonally by adjusting the circuit components. The natural frequency can also be controlled electronically by adjusting the bias currents of the OTAs. For realising all the five standard filtering functions, no critical-matching conditions are imposed and all the incremental parameter sensitivities are low. Experimental and simulation results that confirm the theoretical predictions are given. © 2013 Copyright Taylor and Francis Group, LLC.
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    Design of electronically tunable first order allpass filter using OTAs with gain controllability
    (2013-12-31)
    Prommas, Thawach
    ;
    ; ;
    Silapan, Phamorn
    This paper presents current-mode first-order allpass filter using three operational transconductance amplifiers (OTAs) and grounded capacitor. The use of grounded capacitor makes the circuit more suitable for integrated circuit implementation. The current gain and phase shift can be independently controlled with electronic method. The circuit has high output impedance which enables easy cascading in the current mode circuits. The PSpice simulation results are depicted. The given results agree well with the theoretical anticipation. © 2013 IEEE.
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    Electronically controlled high input and low output impedance voltage mode multifunction filter with grounded capacitors
    (2014-12-01)
    Ninsraku, Wilas
    ;
    Biolek, Dalibor
    ;
    ; ;
    In this study, a three-input single-output voltage-mode biquadratic filter employing voltage differencing differential input buffered amplifier (VD-DIBA) is presented. The proposed filter uses two VD-DIBAs and two grounded capacitors without any external resistors, which is well suited for integrated circuit implementation. The circuit provides five standard transfer functions, namely, low pass, high pass, band pass, notch and all pass filters with electronic control of quality factor and pole frequency. Each transfer function can be selected by suitably selecting input signals via digital method. The filter does not require inverting of the input voltage signal. Moreover, the circuit possesses high input and low output impedances and thus it enables simple voltage-mode cascading. The PSPICE simulation and also experimental results are included, verifying the workability of the proposed filter. The given results agree well with the theoretical anticipation.
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    Temperature Insensitive Current-Mode Four Quadrant Multiplier Using Single CFCTA
    A four quadrant multiplier of two current input signals using active building block, namely current follower cascaded transconductance amplifier (CFCTA) is presented in this paper. The proposed multiplier consists of only single CFCTA without the use of any passive element. The presented circuit has low impedance at current input node and high impedance at current output node which is convenient for cascading in current mode circuit without the need of current buffer circuits. The output current can multiply two input currents with temperature insensitivity. Moreover, the magnitude of output current can be controlled electronically via DC bias current. With only single active building block, the presented multiplier is suitable for integrated circuit implementation for analog signal processing. Simulation results from a PSpice program are presented in order to demonstrate the multiplier proposed here.
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    New quadrature sinusoidal oscillator with amplitude controllability
    (2014-01-01)
    Chandee, Sasithon
    ;
    ; ;
    Pookrongtong, Nattapon
    ;
    Kwawsibsam, Adisorn
    The quadrature sinusoidal oscillator employing two voltage differencing tranconductance amplifiers (VDTAs) has been proposed. The condition of oscillation (CO) and frequency of oscillation (FO) can be independently controlled by adjusting the bias current of two VDTAs. The oscillator can provide two output voltages as quadrature waveform and one output current with magnitude controllability. It consists of two VDTAs and two grounded capacitors which is then suitable for IC architecture. The Pspice simulation results using 0.25μm TSMC CMOS parameters have justified the theoretical anticipation. © 2014 IEEE.
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    Three-inputs single-output voltage-mode universal filter with orthogonal control using single commercially available IC
    In this study, a new electronically tunable voltage-mode second-order universal filter as a new application for commercially available IC named LT1228 from Linear Technology Inc is presented. The proposed filter with three-inputs and single output voltage uses single LT1228, two resistors and two capacitors, which is well suited for off-the-shelf implementation. The proposed filter can provide high pass (HP), low pass (LP), band pass (BP), band reject (BR) and all pass (AP) responses with electronic control of the quality factor (Q) and the natural frequency (ω0). The control of quality factor can be done without affecting natural frequency. The selection of filter response can be done without any critical passive component matching conditions and double gain amplifier circuit. A number of simulations based on PSPICE program are achieved in order to demonstrate the performance of the proposed filter.