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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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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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Reconfigurable Voltage-Mode First-Order Multifunction Filter Employing Second-Generation Voltage Conveyor (VCII) With Complete Standard Functions and Electronically Controllable Modification
(2023-01-01)
Jaikla, Winai
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Sangyaem, Surasak
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Supavarasuwat, Piya
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Khateb, Fabian
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Minaei, Shahram
In this contribution, the realization of a first-order, two-input, single-output voltage-mode multifunction filter employing a second-generation voltage conveyor (VCII) is described. The proposed first-order versatile filter is extremely simple, composed of a single VCII and three passive devices. Because of its low output impedance, the output voltage node can be easily cascaded with other voltage-mode configurations without the requirement of any buffers. In the same circuit topology, the proposed first-order filter provides various filtering functions: inverting and non-inverting low-pass (LPF), inverting and non-inverting high-pass (HPF), as well as inverting and non-inverting all-pass (APF). The digital method allows the selection of output first-order filtering functions without the need for additional circuits such as inverting or double-gain amplifiers. Furthermore, the pass-band gain of the low-pass and high-pass responses can be adjusted by varying the resistance or capacitance values without influencing the pole frequency as well as the phase response. The influence of VCII's current/voltage gain errors and parasitic elements on filtering performance is also investigated. Moreover, the modification of the proposed lagging phase all-pass filter to achieve electronic controllability is also proposed by replacing the passive resistor with the operational transconductance amplifier (OTA). The 0.18μm TSMC CMOS structure of the VCII employed in the proposed filter operates in the subthreshold region and utilizes the bulk-driven technique (BD), enabling it to operate with 0.4V supply voltage and consuming 383 nW of power. The total harmonic distortion (THD) of the LPF with an applied input voltage Vinpp=300 mV @ 50Hz is -49.5 dB. An application example as a quadrature sinusoidal oscillator realized from the proposed first-order allpass filter and lossless integrator is also included. The performance of the proposed reconfigurable voltage-mode first-order filter is simulated and experimentally tested using a commercially available AD844 IC-based VCII with ±5 V power supply.
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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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Single VDDDA-Based Lossy Inductance Simulator for Application to Sinusoidal Oscillator
(2023-01-01)
Jaikla, Winai
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Siripongdee, Surapong
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Sotner, Roman
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Suwanjan, Peerawut
This work presents the design of a new grounded lossy inductance simulator. The proposed circuit emulates an inductor in parallel with a negative resistor, making it applicable to the design of a sinusoidal oscillator. The proposed simulator comprises a voltage differencing differential difference amplifier (VDDDA), a resistor, and a grounded capacitor. The proposed active inductor necessitates no essential matching criteria for passive elements. The equivalent inductance and negative resistance can be controlled electronically. Moreover, the parallel RLC and negative resistance configuration-based sinusoidal oscillator is designed as an example of its application. The oscillation frequency and condition are adjusted orthogonally. The performance of the proposed simulator circuit and the sinusoidal oscillator is evaluated using Pspice simulation and experimentation with VDDDA built from ICs AD830 and LM13700. The simulation and experimental results validate the behavior of the theory.

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