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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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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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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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Electronically Tunable Grounded and Floating Capacitance Multipliers Using a Single Active Element
(2024-01-01)
Seechaiya, Nuttapon
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Jaikla, Winai
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Chaichana, Amornchai
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Silapan, Phamorn
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Supavarasuwat, Piya
A capacitance multiplier is an active circuit designed specifically to increase the capacitance of a passive capacitor to a significantly higher capacitance level. In this paper, the use of a voltage differencing differential difference amplifier (VDDDA), an electronically controllable active device for designing grounded and floating capacitance multipliers, is proposed. The capacitance multipliers proposed in this study are extremely simple and consist of a VDDDA, a resistor, and a capacitor. The multiplication factor (Kc) can be electronically controlled by adjusting the external bias current (IB). It offers an easy way of controlling it by utilizing a microcontroller for modern analog signal processing systems. The multiplication factor has the potential to be adjusted to a value that is either less than or greater than one, hence widening the variety of uses. The grounded capacitance multiplier can be easily transformed into a floating one by utilizing Zc-VDDDA. PSpice simulation and experimentation with a VDDDA realized from commercially available integrated circuits were used to test the performance of the proposed capacitance multipliers. The multiplication factor is electronically adjustable, ranging in approximation from 0.56 to 13.94. The operating frequency range is approximately three frequency decades. The realization of the lagging and leading phase shifters using the proposed capacitance multiplier is also examined and proven. The results reveal that the lagging and leading phase shifts are electronically tuned via the multiplication factor of the proposed capacitance multipliers.
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APPLICATION PROGRAM FOR RESEARCH STANDARD APPLIED: A CASE STUDY OF KING MONGKUT’S INSTITUTE OF TECHNOLOGY LADKRABANG
(2024-01-01)
Thipayasothorn, Pastraporn
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Chaichana, Amornchai
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Phetsinchorn, Aueamaumporn
Conducting research or experiments on humans and creatures has contributed to advancement in science and modern healthcare, and that definitely enables us to have a better life quality. Considering the research standard as the key guidelines and criteria for a single standard research system management, the present research that was carried out at King Mongkut’s Institute of Technology Ladkrabang, Thailand, aimed to understand the operation of the research standard and research ethics of educational institutions and to design an application program on a smartphone to follow up the aforementioned research standard and research ethics. This research consisted of three different stages; that is, Stage One involved surveying the operation of the research standard and research ethics of educational institutions; Stage Two focused on designing an application program on a smartphone to follow up the research standard and research ethics; and Stage Three was the pilot study and evaluation for an efficacy of the application program. The research findings were greatly essential for stakeholders in gaining more knowledge about ethical research practices in humans and promoting information about the operation in the research standard and research ethics of educational institutions in order to keep the research procedures secured and conduct research underlying the ethical and appropriate academic practice.
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Classroom Management as Virtual World for Creating Professional Teaching Environment
(2024-01-01)
Thipayasothorn, Pastraporn
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Chaichana, Amornchai
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Phetsinchorn, Aueamaumporn
Research and innovation for community or local development, aims at providing the individuals with a high quality of life and enhancing capabilities for competition through collaborative efforts of stakeholders, including beneficiaries in the area, especially the academic sector of which powerful educational institutions in the central and metropolitan areas of Thailand. Innovation in vocational education management through online teaching environments intends to have educational innovations in the central and metropolitan areas as a mechanism and process of educational reform that can manage online teaching in line with the local context. This involves flexible and adaptable management that eliminates the need for travel and reduces consumption of resources. This is achieved by research objective of 1) developing innovations in vocational education management through online teaching environments to enhance educational efficiency, 2) reducing educational quality disparities by designing virtual reality training centers for professional skill development, with a case study in the field of art and design, and 3) developing mechanisms for collaborative education management in the community, through the design and use of application programs to create a professional teaching environment. Therefore, this research and innovation in vocational education management in the central region of Thailand through online teaching environments can enhance self-directed learning. This involves designing and developing learning technology, creating a virtual world to establish a professional teaching environment, and innovating learning application programs from 400 sampling. The education system in this changing crisis has a responsibility to stimulate and revive the grassroots economy after the crisis. This emphasizes the crucial role of education as a continuous tool in building economic and social resilience later.
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Electronically Tunable Capacitance Multiplier Implemented Using a Single Active Element for Low-Frequency Biomedical Applications
(2024-01-01)
Chaichana, Amornchai
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Suwanjan, Peerawut
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Siripongdee, Surapong
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Jaikla, Winai
An active circuit designed for increasing a passive capacitor's capacitance to a noticeably larger level is called a capacitance multiplier. The article proposes the design of a grounded capacitance multiplier using an electronically adjustable active device called a voltage differencing differential difference amplifier (VDDDA). The proposed capacitance multiplier is a very compact structure that consists of just one passive resistor, one passive capacitor, and one VDDDA. The multiplication factor (KC) can be electronically controlled by adjusting the external bias current (IB) of VDDDA, which is convenient for microcontroller control in modern analog signal processing systems. To test the performance of the proposed capacitance multipliers PSpice simulation and experimentation using a VDDDA built from commercially available integrated circuits were utilized. To further illustrate the usefulness of the proposed capacitance multiplier, an application example in the lagged phase shifter with electronically adjustable phase shifts is shown and examined.
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MULTIPLE-INPUT SINGLE-OUTPUT VOLTAGE-MODE MULTIFUNCTION FILTER BASED ON VDDDAS
(2023-12-01)
Huaihongthong, Pintira
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Suwanjan, Peerawut
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Siripongdee, Surapong
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Jaikla, Winai
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Chaichana, Amornchai
In recent years, the voltage differencing differential difference amplifier (VDDDA) has been used in various analog signal processing circuit designs. A second-order multifunction filter with multiple-inputs and single-output (MISO) voltage mode using VDDDA as active elements is proposed in this paper. The structure of the proposed filter comprises two VDDDAs, two grounded capacitors, and two resisters. The proposed filter has a cascadability feature in a voltage-mode sys-tem, producing voltage input and voltage output at high and low impedance ports, respectively. It can offer responses for all-pass (AP), band-reject (BR), band-pass (BP), low-pass (LP), and high-pass (HP) filters without additional inverting and double gain amplifiers, as well as the matching conditions. Choosing the appro-priate input signals provides these five filter responses in the same circuit topology. With two VDDDAs, the bias currents can be utilized to electronically tune the natural frequency (ω<inf>0</inf>) independently from the quality factor (Q). Experimental results using available com-mercial ICs have supported the theoretical expectations and confirmed the practical operation of the proposed multifunction biquad filter.
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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
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Jaikla, Winai
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Chaichana, Amornchai
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Suwanjan, Peerawut
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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
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Jaikla, Winai
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Siripongdee, Surapong
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Sotner, Roman
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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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