Voltage Differencing Gain Amplifier Research Articles

Single VDGA-Based Mixed-Mode Electronically Tunable First-Order Universal Filter.

This article presents a mixed-mode electronically tunable first-order universal filter configuration employing only one voltage differencing gain amplifier (VDGA), one capacitor, and one grounded resistor. With the appropriate selection of the input signals, the proposed circuit can realize all three first-order standard filter functions, namely low pass (LP), high pass (HP), and all pass (AP), in all four possible modes, including voltage mode (VM), trans-admittance mode (TAM), current mode (CM), and trans-impedance mode (TIM), from the same circuit structure. It also provides an electronic tuning of the pole frequency and the passband gain by varying transconductance values. Non-ideal and parasitic effect analyses of the proposed circuit were also carried out. PSPICE simulations and experimental findings have both confirmed the performance of the design. A number of simulations and experimental observations confirm the viability of the suggested configuration in practical applications.

A linearly/electronically controllable high gain VDGA and its applications

Since the transconductance gains of an active building block namely voltage differencing gain amplifier (VDGA) is directly proportional to nonlinear (square root) function of external DC bias currents, affecting the narrow range tunability and low transconductance gains. This article aims to introduce a high gain VDGA by using CMOS current squaring circuits biasing in each transconductance cell. It offers high transconductance gains, wide range of tunability, linearity of controllability, larger input voltage range and nearly infinite input impedance. The proposed circuit was designed using a 0.18 µm CMOS transistors technology. The test was performed using PSpice program, it is consistent with the theoretical expectation. The total power consumption is 2.9 mW at ±1.5 V power supply. Even its power consumption is more than about 3 times of their previously proposed VDGAs, the figure of merit (FOM) of the proposed VDGA is much better than that of the previously proposed VDGAs (about 10 times). Additionally, the applications of the proposed VDGA as a capacitance multiplier, current multiplier/divider, summing amplifier, independently/electronically tunable multifunction filter, precision half-wave and full-wave rectifiers are included to insist the workability of the proposed VDGA.

Single VDGA-Based Mixed-Mode Universal Filter and Dual-Mode Quadrature Oscillator.

This article presents the circuit designs for a mixed-mode universal biquadratic filter and a dual-mode quadrature oscillator, both of which use a single voltage differencing gain amplifier (VDGA), one resistor, and two capacitors. The proposed circuit has the following performance characteristics: (i) simultaneous implementation of standard biquadratic filter functions with three inputs and two outputs in all four possible modes, namely, voltage-mode (VM), current-mode (CM), trans-admittance-mode (TAM), and trans-impedance-mode (TIM); (ii) electronic adjustment of the natural angular frequency and independently single-resistance controllable high-quality factor; (iii) performing a dual-mode quadrature oscillator with simultaneous voltage and current output responses; (iv) orthogonal resistive and/or electronic control of the oscillation condition and frequency; (v) employing all grounded passive components in the quadrature oscillator function; and (vi) simpler topology due to the use of a single VDGA. VDGA non-idealities and parasitic elements are also investigated and analyzed in terms of their influence on circuit performance. To prove the study hypotheses, computer simulations with TSMC 0.18 μm CMOS technology and experimental confirmatory testing with off-the-shelf integrated circuits LM13600 have been performed.

Systematic realisation of inductorless and resistorless Chua’s chaotic oscillator using VDGA

ABSTRACT This paper presents an implementation of inductorless and resistorless Chua’s chaotic oscillator using voltage-differencing gain amplifier (VDGA). The chaotic oscillator circuit is implemented by designing a resistorless Chua’s diode using a single VDGA and a VDGA-based tank oscillator with coupled network circuit. The proposed chaotic oscillator uses two VDGAs and three grounded capacitors only. Although resistors and inductors may also be fabricated, the use of no resistor and inductor makes the circuit suitable for fabrication in terms of cost and area. It offers the advantages of an increased frequency spectrum having a dominant operating frequency of 21.1 MHz. The Chua’s circuit is simulated in Pspice using both macro models of IC MAX435 and 0.18 µm CMOS TSMC Technology parameters. As a result, chaotic waveforms (V1 and V2) and the various attractors (V1 versus V2) are found in the simulation. These results confirm the theoretical predictions of Chua’s chaotic oscillator. Various aspects of the proposed implementation of Chua’s oscillator are compared with the earlier implementations. Finally, the paper concludes with simple remarks on the proposed circuit.

A fully/electronically controllable voltage-mode Schmitt trigger based on only single VDGA and its applications

This article is objected to present a new fully/electronically controllable voltage-mode Schmitt trigger based on a modified voltage differencing gain amplifier (VDGA). It can offer both counterclockwise (CCW) and clockwise (CW) functions, without changing circuit topology. The proposed Schmitt trigger comprises merely one VDGA and three resistors. The hysteresis and amplitude of the output voltage of proposed Schmitt trigger can be independently controlled by corresponding bias currents of the VDGA. The modified VDGA was designed by a fully balanced differential transconductance technique based on 0.35 µm CMOS transistor technology, providing advantages in high gain, wide range of adjustability and symmetrical output signals. The performances of proposed Schmitt trigger were deeply investigated by not only simulation via PSpice program, but also experimental setup using commercially available integrated circuits. Both results agree well with the theoretical anticipation and are consistent each other. The total power consumption is approximately 1.39 mW at ± 1.5 V power supply. Additionally, to prove the practical use-abilities of the proposed Schmitt trigger, its applications in a voltage-mode relaxation oscillator, a triangular/square wave generator and a pulse width modulator are also included.

Dual-mode multifunction filter realized with a single voltage differencing gain amplifier (VDGA)

This article presents the dual-mode multifunction biquad filter realized employing only a single voltage differencing gain amplifier (VDGA), one resistor and three capacitors. The proposed filterwith one input and three outputs can configure as voltage-mode or current-mode filter circuit with the appropriate input injection choice. It can also synthesis the three standard filter functions, which are highpass, bandpass, and lowpass responses without modifying the circuit configuration. Orthogonal adjustment between the natural angular frequency (o) and the quality factor (Q) of the filter is achieved. Detail analysis of non-ideal VDGA effects and circuit component sensitivity are included. The circuit principle is verified by means of simulation results with TSMC 0.35-m CMOS process parameters.

Single VDGA-Based Dual-Mode Multifunction Biquadratic Filter and Quadrature Sinusoidal Oscillator

This article relates to the realization of voltage-mode and/or current-mode multifunction biquadratic filter and quadrature oscillator circuits each using one voltage differencing gain amplifier (VDGA), two resistors and two grounded capacitors. The proposed dual-mode filter having one output and three inputs can provide the three standard biquadratic transfer functions with both voltage and current output filter responses simultaneously. It also has the independent tuning of the angular resonance frequency and the quality factor . With a slight modification of the proposed filter, a new dual-mode quadrature sinusoidal oscillator can be obtained. The proposed quadrature oscillator provides orthogonal resistive/electronic control of both oscillation condition and oscillation frequency. Non-ideal and parasitic conditions are also examined and their effects on the circuit performance are discussed. In order to confirm the theory, several computer simulation results with PSPICE program are given .

Condition of phase angle for a new VDGA-based multiphase variable phase shift oscillator from 0<sup>o</sup> to 90<sup>o</sup>

A novel interesting type of variable phase angle voltage mode oscillator using modern building block has been presented in this paper. The new proposed oscillator configuration which uses four voltage differencing gain amplifier (VDGA) and two grounded capacitors can generate two sinusoidal signals that change out of phase by 0 to 90 degree. It has four floating and explicit voltage mode outputs where every two outputs have the same phase. The circuit is characterized by (i) the condition of phase angle of the oscillation (PO) (this concept is introduced for the first time in this paper) can be tuned electronically (ii) the gain of the floating outputs can be controlled independently (iii) it provides electronic control of condition of oscillation (CO) and independent control of frequency of oscillation (FO). The Total Harmonic Distortion (THD) of the output waveforms was obtained and the results were reasonability values (less than 4.5%). The non-ideal analysis and simulation results are investigated and confirmed the theoretical analysis based upon VDGAs implementable in 0.35μm CMOS technology. Simulation results include time response and frequency response outputs generated by using the PSPICE program.

Electronically Adjustable Capacitance Multiplier Circuit with a Single Voltage Differencing Gain Amplifier (VDGA)

In this work, we propose a resistorless realization of the simple capacitance multiplier circuit with electronically controllable using a single voltage differencing gain amplifier (VDGA) as an active building block. The circuit utilizes one VDGA and only one capacitor in a simple circuit configuration. The proposed capacitance multiplier circuit can be tuned electronically with the adjustment of the transconductance gains of the VDGA. To emphasis the workability of the proposed circuit, the second-order RC low-pass filter is constructed as an application example. PSPICE simulations are performed to verify the theory.

Compact electronically tunable quadrature oscillator using single voltage differencing gain amplifier (VDGA) and all grounded passive elements

This work deals with the design of a compact electronically tunable sinusoidal quadrature oscillator. The proposed quadrature oscillator is designed with a single voltage differencing gain amplifier (VDGA) and all the three grounded passive elements. Its oscillation condition and oscillation frequency can be tuned independently by means of the VDGA transconductance gains. The proposed oscillator also provides the explicit quadrature voltage outputs of almost equal magnitude and low active and passive sensitivity figures. The performance of the oscillator has been demonstrated by PSPICE simulations based on TSMC 0.35-$\mu $m CMOS technology.