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    Synthesis of electronically tunable multifunction biquad filter using voltage differencing differential input buffered amplifiers
    (2025-02-01)
    Bunrueangsak, Sirigul
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    Biquad filters are commonly used in analog circuits for various purposes in signal processing and communication applications. We synthesize an analog active biquad filter with five types of voltage-mode filtering functions. The filter is synthesized using a parallel passive resistor-inductor-capacitor (RLC) network and unity-gain voltage differencing amplifier. A voltage differencing differential input buffered amplifier (VD-DIBA) is the main active component, and the biquad filter has a three-input single-output (TISO) topology. By replacing the passive inductor and resistor with VD-DIBA-based inductance and resistance simulators with a subtractor, the TISO voltage-mode versatile filter is obtained from two VD-DIBAs, one resistor, and two capacitors connected to the ground. The proposed filter can provide five types of voltage-mode filtering functions: inverting bandpass and lowpass responses as well as noninverting band-stop, high-pass, and all-pass responses. The all-pass filter requires no additional active components. The three input voltage nodes have high impedance, and a low-impedance output voltage node facilitates cascade connections without using additional voltage buffers. In addition, the natural frequency and quality factor can be electronically tuned. The quality factor is controlled without disturbing the passband gain and natural frequency. The proposed filter is simulated and verified experimentally in the Personal Simulation Program with Integrated Circuit Emphasis (PSPICE) and through laboratory tests employing VD-DIBAs implemented using commercially available components.
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    Single Active Element Based Electronically Controllable Capacitance Multiplier
    (2022-07-15) ;
    Huaihongthong, Pintira
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    The realization of capacitance multiplier using the versatile active building block, namely voltage differencing differential difference amplifier (VDDDA) is presented in this paper. The realized capacitance multiplier is very simple consisting of one VDDDA, one MOS resistor (RM) and one grounded capacitor which is attractive for integration. The multiplication factor (KC) of the realized circuit can be electronically controlled via the bias current (IB) and control voltage (VC) without the need of any matching condition of active and passive element. Moreover, the multiplication factor can be adjusted to be more or less than one. The performances of the presented capacitance multiplier are verified through Pspice simulation using CMOS VDDDA in 0.18μm TSMC technology with ±0.9V power supplies. The multiplication factor is designed to be KC=2 by choosing VC=0.85V, IB=50μA and C=30 pF. The simulated multiplication factor is around 1.98. The simulated operational frequency range is around three decades (6.16 kHz-8.91MHz). The performances of the proposed circuit are also verified by the experiment using VDDDA implemented from the commercial ICs, AD830 and LM13700 with ±5V power supplies. The experiment is conducted under the same multiplication factor (KC=2) as the simulation by choosing RM=0.27 kω (1% passive resistor), IB=96.2μA and C=1nF. The experimental multiplication factor is around 2.06. The experimental operational frequency range is around three decades (1kHz-1.25MHz). By adjusting the bias current from 17.67μA to 400 μA, the experimental multiplication factor is controllable from 11.47 to 0.48. The percent deviation of the theoretical and experimental multiplication factor is lower than 5% when the value of bias current is greater than 39μA. These deviations stem from the effect of the parasitic capacitance and resistance in VDDDA. Moreover, the application example of the presented capacitance multiplier as the sinusoidal oscillator is presented. The performances of the presented oscillator verified via the experiment are well consistent with theoretical anticipation.
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    Item type:Publication,
    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
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    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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    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
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    Sotner, Roman
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    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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    Electronically Adjustable Voltage-mode First-order Allpass Filter Using Single Commercially Available IC
    In this design, the use of single commercially available integrated circuit (IC), LT1228 from Linear Technology Corporation, to implement the first order allpass filter is presented. The passband voltage gain of the presented first allpass filter (APF) is unit and constant throughout the operation frequency, while the phase response is electronically tuned by changing the external DC bias current. With this property, the proposed first order filter can be used as phase shifter with microcontroller controllability. Tuning phase property is not required any matching condition. The proposed phase shifter consists of one LT1228, one capacitor and two resistors which is attractive for off the shelf implementation. Moreover, the impedance at output voltage node is exhibit low which can connect to other circuit without the requirement of external voltage buffer. The expected performances of the proposed circuit are proved by Pspice simulation using macro model parameters. Also, the quadrature sinusoidal oscillator which is designed from the connecting of the proposed filter and integrator is chosen as application example.
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    Item type:Publication,
    Electronically Tunable TISO Voltage-Mode Universal Filter Using Two LT1228s
    (2022-01-01)
    Wai, May Phu Pwint
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    This study aims to design an electronically tunable voltage-mode (VM) universal filter utilizing commercially available LT1228 integrated circuits (ICs) with three-input and single-output (TISO) configuration. With the procedure based on two integrator loop filtering structures, the proposed filter consists of two LT1228s, four resistors, and two grounded capacitors. It realizes five filter output responses: low-pass, all-pass, band-reject, band-pass, and high-pass functions. By selecting input voltage signals, each output responses can be achieved without changing the circuit architecture. The natural angular frequency can be controlled electronically. The input voltage nodes Vin1 and Vin3 possess high impedance. The output node has low impedance, so it can be cascaded to other circuits. The performance of the proposed filter is corroborated by PSpice simulation and hardware implementation which support the theoretical assumptions. The result shows that the range of total harmonic distortion (THD) is lower than 1%, and that the higher the temperature is, the lower the natural angular frequency is.
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    Item type:Publication,
    Design of Electronically Controllable Multifunction Active Filter with Amplitude Controllability Using Two Commercially Available ICs
    (2022-01-01)
    Onanong, Narumol
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    Angamnuaysiri, Daungkamol
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    In this contribution, the design and analysis of an active multifunction biquad filter that provides five voltage-mode filtering configurations in the same core filtering circuit are presented. The design emphasizes using the commercially available ICs, LT1228, which are easy for off-the-shelf implementation and cheaper compared with the chip implementation. The proposed multifunction filter is realized from two commercial LT1228 ICs as the active function block, combined with five passive elements (three resistors and two capacitors) with three input voltage nodes and a single output voltage node. The following advantages are given for this design: (i) it provides high-pass (HP), low-pass (LP), band-stop (BS), band-pass (BP), and all-pass (AP) filtering functions; (ii) orthogonal and electronic tuning of the natural frequency ω0 and bandwidth (the quality factor: Q); (iii) output voltage node of the proposed circuit is low impedance; (iv) passband voltage gain is controllable; and (v) matching condition and extra double gain voltage-mode amplifier are not required. The effect of the parasitic element in LT1228 on the filter performance is analyzed and included to strengthen the design idea. The PSpice simulation results using LT1228 with ±5 V and the experimental results tested from the hardware implementation are given to prove the validity of the designed multifunction filter.
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    One input voltage and three output voltage universal biquad filters with orthogonal tune of frequency and bandwidth
    (2021-08-01)
    Wai, May Phu Pwint
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    This research paper contributes the one input three output voltage mode universal biquad filters with linear and electronic control of the natural frequency (ω0), using two commercially available ICs, LT1228s as active device with two grounded capacitors, five resistors. The presented universal biquad filters can simultaneously provide three voltage-mode filtering functions, low-pass (LP), high-pass (HP) and band-pass (BP) without changing the circuit architecture. Furthermore, the first presented biquad filter provides low impedance at HP, BP voltage output nodes and LP, BP output voltage nodes are low impedance for the second proposed filter which is easy cascade ability with other voltage mode circuits without the employment of buffer circuits. The quality factor (Q) of both proposed filters is orthogonally adjusted from the passband voltage gain and ω0. The proposed filters are simulated and experimented with commercially accessible ICs, LT1228. The simulated and experimental results demonstrate the filtering performances.
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    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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    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.