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    Single commercially available ic-based electronically controllable voltage-mode first-order multifunction filter with complete standard functions and low output impedance
    (2021-11-01) ;
    Buakhong, Unchittha
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    ;
    Khateb, Fabian
    ;
    Sotner, Roman
    This paper presents the design of a voltage-mode three-input single-output multifunction first-order filter employing commercially available LT1228 IC for easy verification of the proposed circuit by laboratory measurements. The proposed filter is very simple, consisting of a single LT1228 as an active device with two resistors and one capacitor. The output voltage node is low impedance, resulting in an easy cascade-ability with other voltage-mode configurations. The proposed filter provides four filter responses: low-pass filter (LP), high-pass filter (HP), inverting all-pass filter (AP−), and non-inverting all-pass filter (AP+) in the same circuit configuration. The selection of output filter responses can be conducted without additional inverting or double gains, which is easy to be controlled by the digital method. The control of pole frequency and phase response can be conducted electronically through the bias current (I<inf>B</inf>). The matching condition during tuning the phase response with constant voltage gain is not required. Moreover, the pass-band voltage gain of the LP and HP functions can be controlled by adjusting the value of resistors without affecting the pole frequency and phase response. Additionally, the phase responses of the AP filters can be selected as both lagging or leading phase responses. The parasitic effects on the filtering performances were also analyzed and studied. The performances of the proposed filter were simulated and experimented with a ±5 V voltage supply. For the AP+ experimental result, the leading phase response for 1 kHz to 1 MHz frequency changed from 180 to 0 degrees. For the AP− experimental result, the lagging phase response for 1 kHz to 1 MHz frequency changed from 0 to −180 degrees. The design of the quadrature oscillator based on the proposed first-order filter is also included as an application example.
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    Item type:Publication,
    Five-inputs single-output voltage mode universal filter with high input and low output impedance using VDDDAs
    (2017-01-01)
    Sangyaem, Surasak
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    ; ;
    Khateb, Fabian
    The design of analog filter using active building block has been gained significant attention and has become an interesting research topic. A five-inputs single −output voltage-mode universal biquadratic filter using active building block, namely voltage differencing differential difference amplifier (VDDDA) is presented in this paper. The proposed filter consists of two VDDDAs and two grounded capacitors. The presented circuit has high impedance for all input voltage nodes and low impedance for output voltage node which is ideal for cascade in voltage-mode circuit without the use of buffer circuits. It can provide five output voltage functions which are band-pass (BP), low-pass (LP), band-reject (BR), high-pass (HP) and all-pass (AP) responses. For high-pass and band-pass functions, the inverting and non-inverting response can be achieved. The matching condition, the inverting and double gain amplifier are not required which is easy to select the output response by digital method. The natural frequency and quality factor can be electronically tuned that is attractive for microcomputer or microcontroller controllability. To verify the validity of proposed filter, the PSPICE simulation and experimental results using VDDDA constructed from commercially available IC are included. The measured results agree well with theoretical expect.
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    Item type:Publication,
    Single-input multiple-output voltage-mode shadow filter based on VDDDAs
    This paper presents a voltage-mode shadow filter with single-input multiple-output (SIMO) configuration using voltage differencing differential difference amplifiers (VDDDAs). In this design, the low-pass and high-pass output functions of the single-input three-output second order filter are feedback via the voltage amplifier. The proposed filter consists of three VDDDAs, one grounded resistor and two grounded passive elements. The proposed filter uses grounded elements which is attractive for integrated circuit (IC) fabrication. It can simultaneously provide low-pass (LP), high-pass (HP), band-pass (BP), band-reject (BR) and all-pass (AP) responses without matching condition. The proposed circuit has high input impedance. The natural frequency (ω <inf>0</inf> ) and quality factor (Q) can be independently and electronically tuned by changing the external DC bias currents. The effect of the non-ideal and parasitic elements of the VDDDA is studied and investigated. The PSpice simulation and experimental results using CMOS technology and commercially available active devices are given to confirm the workability of the proposed filter.
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    Item type:Publication,
    Synthesis of biquad filters using two VD-DIBAs with independent control of quality factor and natural frequency
    (2021-04-01) ; ;
    Khateb, Fabian
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    Sotner, Roman
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    Silapan, Phamorn
    This contribution presents the procedure to synthesis the voltage-mode active biquad filters using the active elements, voltage differencing differential input buffered amplifier (VD-DIBA). Two filtering categories, single input four output (SIFO) configuration and three input three output (TITO) configuration are proposed. Both proposed filters consist of two VD-DIBAs, two grounded capacitors and two resistors. All input voltage nodes for both biquad filters exhibit high impedance. The proposed SIFO biquad filter simultaneously provide four filtering responses, low pass (LP), band pass (BP), high pass (HP) and band reject (BR) functions, while the proposed TITO filter provides five filtering responses (including all pass (AP) function). The natural frequency (ω<inf>0</inf>) is linearly and electronically tuned without affecting the quality factor (Q). Also, the Q adjusting can be done without affecting the ω<inf>0</inf>. By modifying the proposed TITO biquad filter, the current controlled sinusoidal oscillator is achieved. The frequency of the generated sinewave is linearly tuned without affecting the condition of oscillation. The performances of the proposed circuits are simulated by Cadence software and the Spectre simulator of the Analog Design Environment using CMOS VD-DIBA in 0.18 μm TSMC CMOS technology and laboratory experiment using VD-DIBA constructed from commercially available ICs.
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    Item type:Publication,
    Electronically tunable current-mode biquad filter employing CCCDTAs and grounded capacitors with low input and high output impedance
    In this study, a single-input multiple-outputs current-mode analog biquadratic filter, based on current controlled current differencing transconductance amplifier (CCCDTA) is presented. The proposed filter uses two CCCDTAs and two grounded capacitors without any external resistors, which is well suited for integrated circuit implementation. The filter simultaneously gives 3 standard transfer functions, namely, lowpass, highpass and bandpass filters with independent control of quality factor and pole frequency by electronic method. By summing of I<inf>HP</inf> and L<inf>LP</inf>, the notch filter can be also achieved. Moreover, the circuit has low input and high output impedance which would be an ideal choice for cascading in current-mode circuit. The PSPICE simulation results are included verifying the workability of the proposed filter. The given results agree well with the theoretical anticipation. © 2013 Elsevier GmbH.
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