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Voltage-Controlled Sinusoidal Oscillator Using Commercially Available ICs with Amplitude Adjustability and Its Application to FM and FSK Modulations for Transmission and Processing of Identified Low-Frequency Signals
(2026-04-01)
Suwanjan, Peerawut
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Adhan, Suchin
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Chaichana, Amornchai
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Sotner, Roman
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Nramat, Wichai
This paper presents a new voltage-controlled sinusoidal oscillator employing only two commercially available LT1228 integrated circuits, four resistors, and two capacitors. The proposed oscillator provides independent control of oscillation frequency and oscillation condition, as well as adjustable output amplitude, while maintaining low output impedance without requiring additional active components. The oscillation frequency is electronically and linearly tuned via the LT1228 bias current or control voltage. Experimental results confirm the practicality of the design: The proposed VCO achieves a wide linear tuning range from 9.25 kHz to 837.2 kHz, THD below 2.55%, and phase noise of –73.35 dBc/Hz at a 1 kHz offset for a 237.8 kHz carrier. The amplitude of the sinusoidal output is adjustable from 0.48 Vp-p to 6.64 Vp-p. In addition, the proposed VCO is successfully applied to FM and FSK modulation for low-frequency signal transmission, and the FM demodulation test yields a recovered sawtooth signal with an SNR of 34.51 dB. Compared with existing LT1228-based oscillators, the proposed circuit achieves 25% lower power consumption (149 mW) and reduces the number of ICs required while improving functional versatility. These results validate the effectiveness and novelty of the proposed LT1228-based design.
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Reconfigurable versatile temperature-insensitivity immittance simulators with electronic tunability using commercially available ICs
(2026-01-01)
Kulapong, Worawut
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Sotner, Roman
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Khateb, Fabian
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Jaikla, Winai
This paper presents novel reconfigurable and electronically tunable immittance simulators using commercially available LT1228 integrated circuits. The proposed circuits simulate four fundamental impedance functions, which are a resistor, a capacitor, an inductor, and a frequency-dependent negative resistor (FDNR) within the same topology. The proposed simulators use only two or three LT1228 ICs and three passive components to provide grounded and floating types, be compact, and function in a variety of ways. A significant contribution of this work is the development of an impedance expression that does not depend on temperature. This makes sure that performance stays stable over a wide range of temperatures without the need for external compensation techniques. The proposed circuits offer linear electronic control via bias currents, enabling precise and dynamic tuning of the simulated element values. Moreover, the proposed simulators can be configured to four lossless impedance functions without needing the matching conditions of passive elements. A study of the parasitic effect is also conducted to assess accuracy and useful frequency range of the proposed configuration. Both grounded and floating configurations are realized and validated through simulation and experimental results. A third-order low-pass ladder filter and a multifunction second-order filter are designed to show the applications of the proposed simulators. The accuracy, reconfigurability, and temperature stability of the proposed circuits are confirmed by the simulation and experimental results, which make them ideal for modern analog signal processing applications. Temperature stability is verified via PSpice simulation over –100 °C to + 100 °C, showing less than 1 % variation, while impedance accuracy and filter applications are confirmed experimentally.
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Design of Constant Phase Elements for Adjustable Pseudocapacitance by a Single Driving Voltage Using Integrated Unipolar Transistor Fields
(2026-01-01)
Sotner, Roman
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Litovska, Anna
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Polak, Ladislav
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Jerabek, Jan
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Kledrowetz, Vilem
This paper presents the design of a passive fractional-order element with tunable pseudocapacitance, enabling adaptable circuit behavior without additional power consumption. This is an important feature for modelling and characterization in natural systems, as well as in the field of electrical and electronic engineering, particularly for the design of instrumentation and sensing systems. The proposed topologies are based on integrated unipolar transistor arrays. Two implementations are demonstrated, with fractional orders of 0.22 and 0.5, offering pseudocapacitance adjustment ranges from 65 to 1 670 mikroF/s^0.78 and from 6.7 to 51 mikroF/s^0.5, respectively. Tuning is achieved through a DC bias voltage ranging from 0.8 to 10 V. The devices operate across nearly two decades of frequency, from approximately 100 Hz to 200 kHz, and support signal amplitudes in the hundreds of millivolts. Two application examples highlight their potential: electronic tuning of the center frequency in a fractional-order band-pass filter, and adjustment of the oscillation frequency in a fractional-order oscillator with a fixed 22.5 degrees phase shift between output waves. All concepts and results are experimentally validated in the laboratory.
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Differentiator circuits with scalable and electronically adjustable time constant and their application in phase shift evaluation
(2025-09-01)
Sotner, Roman
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Polak, Ladislav
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Petrzela, Jiri
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Semenov, Dmitrii
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Langhammer, Lukas
Two novel scalable and electronically adjustable differentiator designs are presented in this paper. These designs are based on special variable gain amplifiers extending well-known concept of standard single operational amplifier-based differentiators. The key novelty lies in their scalability, which allows for an enhanced time constant value by adjusting the ratio of resistors. Simultaneously, the special form of gain control using a DC voltage offers wide electronic tunability. The solution performs high input and low output impedance, both independent of frequency. Experimental testing demonstrated time constant adjustments in two configurations: from 64 ns to 4.5 µs (a ratio of maximal and minimal value 70) and from 8.7 µs to 183 µs (a ratio of 21). As an application example, the proposed differentiator is utilized in the design of a readout system for an absolute phase shift difference to pulse width ratio converter, suitable for monitoring a very slow phenomenon such biosignals.
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Electronically controlled square/triangular wave generator with amplitude adjustability and its application in light intensity measurement using commercial-off-the-shelf current feedback amplifiers
(2025-07-01)
Choykhuntod, Pawich
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Sotner, Roman
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Silapan, Phamorn
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Kaewon, Rapeepan
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Jaikla, Winai
This study presents a square and triangular waveform generator using two commercial-off-the-shelf current feedback amplifiers with DC gain control, LT1228. The frequency of the square and triangular waveforms can be electronically and independently adjusted with the bias current. With this advantage feature, the proposed generator can be easily modified to generate a sawtooth waveform and electronically adjust the duty cycle of square waves. Additionally, PWM signals can also be generated from the proposed circuit. The amplitude of both square and triangular waveforms is adjustable without affecting the frequency, and the output nodes have low impedance. The circuit's performance is validated through practical implementation and testing, showing excellent agreement with theoretical analysis. The measured linear and electronic adjustment of frequency spanned from 4.83 kHz to 436.2 kHz. Furthermore, the circuit can be applied as a low-cost light intensity detection sensor.
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Second-generation voltage conveyor-based first-order all-pass filters and application to quadrature sinusoidal oscillator
(2025-02-01)
Jaikla, Winai
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Theppota, Burin
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Saksiri, Wiset
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Khateb, Fabian
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Siripruchyanun, Montree
This article describes 2 first-order voltage-mode all-pass filters (APFs) covering leading and lagging phases based on single capacitor and second-generation voltage conveyors (VCIIs). The proposed APFs comprise 2 VCIIs cooperating with 3 resistors and 1 capacitor. The phase angle of the output relative to input signals can be tuned by the single external resistor. Different from previously related works, they use only VCII+ which can be easily realized and less complicated for both integrated circuit architecture and off-the-shelf design. In addition, a 450 mV 1.98 µW VCII based on bulk-driven quasi-floating-gate MOS transistor was developed to be used in this work to achieve ultra low-voltage and low-power consumption. The proposed APFs offer a phase shifting function over a wide range of operating frequency. Its output also provides an accurate sinusoidal signal. The testing results obtained from Cadence Virtuoso System Design Platform simulation are disclosed to investigate different behaviors of the proposed APFs. In addition, the experimental setup using commercially available integrated circuits is shown. From the both results, it is found that they are agreed well with the mentioned anticipations. An application of the proposed APFs in quadrature sinusoidal oscillator is also depicted, it enjoys independent controllability of oscillation condition and oscillation frequency for a wide range of operating frequency with a precise quadrature output signal.
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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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Jaikla, Winai
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Chaichana, Amornchai
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Supavarasuwat, Piya
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Siripongdee, Surapong
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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A First-order All-pass Filter Based on LT1228 and Its Application
(2025-01-01)
Puengchaipat, Akanut
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Satayachiti, Pittawat
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Piromlith, Natchapon
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Jaikla, Winai
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Kaewon, Rapeepan
This paper proposes a first-order all-pass filter (APF) that employs two LT1228s, a resistor, and a grounded capacitor to be implemented via commercially available integrated circuits. The phase response of the proposed filter is electronically controllable by modifying the transconductance value via the biasing current of the OTA (IB1). The oscillator quadrature sinusoidal signal circuit is generated by the proposed APF, which includes an integrator. The efficacy of the sinusoidal oscillator circuit and the proposed APF is validated through the use of experimental results and simulations. The results that were obtained are in strong agreement with the theoretical predictions.
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Voltage-Mode First-order Multifunction Filter with Electronic Controllability Using VDDDA
(2025-01-01)
Chaleekrua, Nitchakan
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Siripruchyanun, Montree
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Jaikla, Winai
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Chaichana, Amornchai
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Suwanjan, Peerawut
This study presents the design of a three-input single-output voltage-mode first-order multifunction filter. The proposed filter comprises a single VDDDA as the active component, one grounded capacitor, and two resistors. The output voltage node has low impedance. The proposed filter provides three responses consisting of a low-pass (LP), a highpass (HP), and an all-pass (AP) by setting the voltage signal at the input voltage. The natural frequency (f<inf>0</inf>) and phase response are electronically controlled by the bias current (I<inf>B</inf>). This flexibility allows for precise tuning of the filter characteristics to meet specific application requirements. The passband gain of LP and HP filters can be adjusted using resistors R<inf>1</inf> and R<inf>2</inf> without affecting the f<inf>0</inf> or requiring an additional amplifier. The simulation and experimental results validate the functionality of the proposed filter as anticipated theoretically. This reliability is crucial for communications and signal processing applications, where accurate signal representation is paramount.
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Single Commercially Available Integrated Circuit-based Sinusoidal Oscillators with Amplitude Adjustability and Electronic Control of Condition
(2024-09-01)
Duangkaew, Suleeporn
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Supavarasuwat, Piya
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Siripruchyanun, Montree
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Sotner, Roman
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Jaikla, Winai
This paper presents four new sinusoidal oscillators using a commercially available integrated circuit (IC). The proposed circuits are simple topologies that employ a single commercial IC, LT1228. It is connected to passive element, consisting of four resistors and two capacitors. All derived oscillator circuits have low output impedance, allowing them to connect to other circuits without requiring an additional buffer. Using an active LT1228 device enables electronic adjustment of parameters in the proposed circuits. A feedback resistor can be used to change the output signal's amplitude without affecting the oscillation's frequency or condition. We performed both simulations using the PSPICE program and experiments to confirm the accuracy of all proposed oscillator circuits. The best total harmonic distortion was 0.13% for the proposed oscillator circuit 3. Adjusting the maximum amplitude using a resistor provides a gain of roughly 1.5–16.5 dB for the proposed oscillator circuit no. 1.

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