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    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
    ;
    Jaikla, Winai
    ;
    Chaichana, Amornchai
    ;
    Suwanjan, Peerawut
    ;
    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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    A New Method to Synthesise the Sinusoidal Oscillator Based on Series Negative Resistance-Capacitance and its Implementation Using a Single Commercial IC, LT1228
    (2023-01-01)
    Kulapong, Worawut
    ;
    Jaikla, Winai
    ;
    Siripongdee, Surapong
    ;
    Sotner, Roman
    ;
    Suwanjan, Peerawut
    An alternative method for synthesising the sinusoidal oscillator based on series negative resistance-capacitance is presented in this paper. The proposed topology is constructed with the series negative resistance-capacitance circuit connected in parallel with a grounded resistor and capacitor. To validate the proposed method, a new grounded series negative resistance-capacitance simulator is also proposed as a subcircuit for synthesising the sinusoidal oscillator. The series negative resistance-capacitance simulator is based on a commercially available integrated circuit (IC), LT1228. The equivalent negative resistance and equivalent negative capacitance can be adjusted electronically using an external DC bias current. The sinusoidal oscillator that is synthesised using the proposed method consists of a single LT1228, two capacitors, and three resistors. The frequency and the condition of the oscillation are orthogonally adjusted. Also, the condition of oscillation is electronically controlled. The amplitude of the sinusoidal waveform is adjustable. In addition, the output voltage node of the proposed oscillator has a low impedance, which allows it to connect to other circuits without using an additional buffer. Both PSPICE simulation and experiment are used to validate the proposed circuits.
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    The voltage-mode first order universal filter using single voltage differencing differential input buffered amplifier with electronic controllability
    (2022-04-01)
    Duangmalai, Danupat
    ;
    Suwanjan, Peerawut
    In this research contribution, the electronically tunable first-order universal filter employing a single voltage differencing differential input buffered amplifier (VD-DIBA) (constructed from two commercially available integrated circuit (IC): the operational transconductance amplifier, IC number LT1228, and the differential voltage input buffer, IC number AD830), one capacitor and two resistors. The features of the designed first order universal filter are as follows. Three voltage-mode first-order functions, low-pass (LP), all-pass (AP) and high-pass (HP) responses are given. The natural frequency (ω<inf>0</inf>) of the presented configuration can be electronically adjusted by setting the DC bias current. Moreover, the voltage gain of the LP and HP filters can be controllable. The phase responses of an AP configuration can be varied from 0<sup>0</sup> to -180<sup>0</sup> and 180<sup>0</sup> to 0<sup>0</sup>. The power supply voltages were set at ±5 V. Verification of the theoretically described performances of the introduced electronically tunable universal filter was proved by the PSpice simulation and experiment.
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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)
    Jaikla, Winai
    ;
    Buakhong, Unchittha
    ;
    Siripongdee, Surapong
    ;
    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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    Electronically and orthogonally tunable sito voltage-mode multifunction biquad filter using lt1228s
    (2021-10-27)
    Wai, May Phu Pwint
    ;
    Suwanjan, Peerawut
    ;
    Jaikla, Winai
    ;
    Chaichana, Amornchai
    The commercially available IC LT1228 is an interesting active device due to its advantage features, such as a fast transconductance amplifier, a wide bandwidth over a wide range of voltage gain, low total harmonic distortion (THD), high impedance differential input, etc. The single-input triple-output (SITO) voltage-mode (VM) multifunction biquadratic filters using ICs, LT1228s are introduced in this research. This circuit design provides the three-filtering functions, low-pass (LP), high-pass (HP), and band-pass (BP), without changing the circuit architecture. It comprises three LT1228s, four resistors, and two capacitors connected to the ground. The low impedance voltage output nodes are HP and BP responses. The quality factor (Q) and the pole frequency (ω0) can be electronically and orthogonally tuned by altering the third LT1228's bias current (IB). The PSPICE simulation and the experiment are verified to describe the circuit operation.
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    Single Input Multiple Output Voltage Mode Universal Filters with Electronic Controllability Using Commercially Available ICs
    (2020-06-01)
    Pwint Wai, May Phu
    ;
    Jaikla, Winai
    ;
    Suwanjan, Peerawut
    ;
    Sunthonkanokpong, Wisuit
    This contribution presents the realization of commercially available ICs based single input voltage and three-output voltages universal second order filters with electronic controllability. Both proposed filters comprise two commercially available ICs LT1228, three passive resistors and two grounded passive capacitors. Two presented filters give low-pass (LP) voltage transfer function, band-pass (BP) voltage transfer function and high-pass (HP) voltage transfer function without modifying the scheme. The filtering parameters, center frequency (ω0) is tuned electronically as well as quality factor (Q) via controlling external DC bias currents. Moreover, the ω0 is linearly and electronically controlled without disturbing the Q by simultaneously changing bias currents. Using grounded capacitors are easy for the cancellation of parasitic element effects in LT1228s. The Pspice simulation and experimental results using integrated circuit, LT1228 are given to verify the filtering design.
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    Current/voltage controlled quadrature sinusoidal oscillators for phase sensitive detection using commercially available IC
    (2020-03-01)
    Jaikla, Winai
    ;
    Adhan, Suchin
    ;
    Suwanjan, Peerawut
    ;
    Kumngern, Montree
    This paper presents the quadrature sinusoidal oscillators for a phase sensitive detection (PSD) system. The proposed oscillators are design by using the commercially available ICs (LT1228). The core oscillator consists of three LT1228s: two grounded capacitors and one resistor. By adding four resistors without the requirement of additional active devices, the amplitudes of two quadrature waveforms become adjustable. The quadrature output nodes are of low impedance, which can be connected to the impedance sensor or other circuits in a phase sensitive detection system without the need of buffer devices. The amplitudes of the quadrature waveform are equal during the frequency of oscillation (FO) tuning. The frequency of oscillation is electronically and linearly controlled by bias current or voltage without affecting the condition of oscillation (CO). Furthermore, the condition of oscillation is electronically controlled without affecting the frequency of oscillation. The performances of the proposed oscillators are experimentally tested with ±5 voltage power supplies. The frequency of the proposed sinusoidal oscillator can be tuned from 8.21 kHz to 1117.51 kHz. The relative frequency error is lower than 3.12% and the relative phase error is lower than 2.96%. The total harmonic distortion is lower than –38 dB (1.259%). The voltage gain of the quadrature waveforms can be tuned from 1.97 to 15.92. The measurement results demonstrate that the proposed oscillators work in a wide frequency range and it is a suitable choice for an instrument-off-the-shelf device.
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    Three-inputs single-output voltage-mode universal filter with orthogonal control using single commercially available IC
    (2017-07-02)
    Suwanjan, Peerawut
    ;
    Siripongdee, Surapong
    ;
    Jaikla, Winai
    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.