Norbert Herencsar

The conception of differential-input buffered and transconductance amplifier (DBTA) and its application

In this paper, a novel versatile active building block the differential-input buffered and transconductance amplifier (DBTA) is proposed. The application of the newly defined active function block is shown on the design of voltage-mode (VM), multi-input and single-output (MISO)-type multifunction biquad, employing single DBTA and five passive elements. Proposed VM filter structure can realize four filter functions i.e., low- (LP), band- (BP), high-pass (HP) and band-stop (BS) without changing the circuit topology and enables independent control of the quality factor Q using single passive element. Theoretical results are verified by PSPICE simulations using a BJT realization of DBTA.

Realisations of single-resistance-controlled quadrature oscillators using a generalised current follower transconductance amplifier and a unity-gain voltage-follower

This article presents realisations of single-resistance-controlled-oscillators (SRCOs) using the recently proposed modern active building block (ABB), namely the generalised current follower transconductance amplifier (GCFTA) and unity-gain voltage-follower (UGVF). The SRCO is made using reduced number of components: one GCFTA and one UGVF as the ABBs, two resistors and two grounded capacitors. The circuit offers the advantage of non-interactive control of condition of oscillation and frequency of oscillation and enjoys low active and passive sensitivities. The circuit is also capable of providing two quadrature voltage outputs. PSPICE simulations have been carried out using the bipolar implementation of the circuits. The simulation results validate the theoretical analysis.

Tuneable filter using voltage conveyors and current active elements

In this article a new structure of the multifunction second-order frequency filter working in current mode is presented. The circuit solution employs voltage conveyors and programmable current amplifiers. The advantage of the proposed circuit is the possibility of mutually independent control of the quality factor Q and pole frequency f 0 using the active elements, current inputs at low-impedance and ground potential, realisation of the low-, high- and band-pass response without changing the circuit topology, low passive and active sensitivities. The frequency filter has been designed using the M-C signal flow graphs and its behaviour verified by OrCAD PSpice simulations.

Single CCTA–Based Universal Biquadratic Filters Employing Minimum Components

—In this paper a new second–order voltage– and current–mode universal biquadratic frequency filters using only single current conveyor transconductance amplifier (CCTA) and four passive elements are presented. The proposed voltage–mode universal filter has been transformed into current–mode universal filter using adjoint transformation method. Proposed circuits enables to realize the low–, band–, high–pass, band–stop and all–pass responses without changing the circuit topology and the possibility of independent control of the quality factor Q using single passive element. No component matching is required and all the passive and active sensitivities are low. PSPICE simulations and experimental results based on commercially available amplifiers OPA861 and MAX435 are included verify the theoretical conclusions of the proposed circuits.

An electronically tunable current-mode quadrature oscillator using PCAs

This article presents a new realisation of active RC sinusoidal oscillator with electronically tunable condition and frequency of oscillation (FO). As compared to the class of three resistors, two capacitors (3R-2C)-based canonic oscillators, the circuit proposed here uses only two resistors and two capacitors as the passive components and still provides non-interactive tuning laws for the condition of oscillation and the FO. The proposed circuit employs new bipolar programmable current amplifier as the active building block and is capable of simultaneously providing two explicit quadrature current outputs. SPICE simulation results have been included to verify the workability of the circuit as an oscillator and the tuning range of the FO.

New voltage-mode universal filter and sinusoidal oscillator using only single DBTA

In this article, a new voltage-mode second-order universal frequency filter and sinusoidal oscillator using only single differential-input buffered and transconductance amplifier (DBTA) is presented. The proposed voltage-mode filter structure using single DBTA and four passive elements can provide all standard filter functions, i.e. low-, band-, high-pass, band-stop, and all-pass without changing the circuit topology and enables independent control of the quality factor Q using single passive element. The circuit requires the minimal number of active and passive elements with no conditions for component matching. By slight modification of the proposed filter structure, the new DBTA-based sinusoidal oscillator is easily obtained. The oscillation condition and the oscillation frequency are independently adjustable by different virtually grounded passive elements. The proposed sinusoidal oscillator employs only grounded capacitors. The passive and active sensitivities of all the proposed circuit configurations are low. PSPICE simulations using a BJT realisation of DBTA and experimental results based on commercially available amplifiers OPA860 and MAX436 are included, which prove the workability of the proposed circuits.

New voltage-mode quadrature oscillator employing single DBTA and only grounded passive elements

A new voltage-mode quadrature oscillator employing single differential-input buffered and transconductance amplifier (DBTA), three grounded capacitors, and two grounded resistors is presented. The use of only grounded capacitors and resistors makes the proposed circuit ideal for integrated circuit implementation. Outputs of two sinusoidal signals with 90° phase difference are available in the proposed quadrature oscillator. The oscillation condition and the oscillation frequency are independently adjustable by different grounded passive elements. The passive and active sensitivities of the proposed circuit configuration are low. PSPICE simulation results are given to verify the theoretical analysis.

A new electronically tunable voltage-mode active-C phase shifter using UVC and OTA

In this paper, a new voltage-mode first-order all-pass filter is presented. The proposed filter provides both of non-inverting and inverting outputs at the same configuration. The circuit is composed of single universal voltage conveyor (UVC), operational transconductance amplifier (OTA), and capacitor. Considering the electronically tunability properties of the OTA phase responses of the proposed active-C circuit can be controlled by an external bias current. The circuit is suitable for wideband applications. All the active and passive sensitivities are low. The theoretical results are verified by PSPICE simulations using BJT implementations of UVC and OTA.

Precise Electronically Adjustable Oscillator Suitable for Quadrature Signal Generation Employing Active Elements with Current and Voltage Gain Control

A new oscillator suitable for quadrature and multiphase signal generation is introduced in this contribution. A novel active element, called the controlled gain-buffered current and voltage amplifier (CG-BCVA) with electronic possibilities for current and voltage gain adjustment is implemented together with a controlled gain-current follower differential output buffered amplifier (CG-CFDOBA) for linear adjustment of the oscillation frequency and precise control of the oscillation condition in order to ensure a stable level of generated voltages and sufficient total harmonic distortion. The parameters of the oscillator are directly controllable electronically. Simultaneous changes of two current gains allow linear adjusting of the oscillation frequency, and a controllable voltage gain is intended to control the oscillation condition. A detailed comparison of the proposed circuits with recently developed and discovered solutions employing the same type of electronic control is provided and shows the useful features of the proposed oscillator and utilized methods of electronic control. Behavioral models based on commercially available ICs have been used for experimental purposes. CMOS implementation of active elements was introduced and utilized for additional simulations and studies. Non-ideal analysis, Monte Carlo statistical evaluations of simulated models, and further analyses were performed for the exact determination of the expected results. Laboratory experiments confirmed the workability and estimated behavior of the proposed circuit as well.

Design of Z-copy controlled-gain voltage differencing current conveyor based adjustable functional generator

This paper introduces interesting active element and its application in the field of square and triangular wave generators. Active element, so-called Z-Copy Controlled Gain Voltage Differencing Current Conveyor (ZC-CG-VDCC), has availability of three mutually independently and electronically adjustable parameters (transconductance, intrinsic resistance of the current input terminal and current gain between two terminals) that are very popular for control of applications today. In addition, a proposed device utilizes very useful z-copy (additional auxiliary terminal) features and two terminals providing voltage difference. All mentioned features are beneficial in mixed-mode circuit synthesis and design of adjustable applications (active filters, oscillators, generators, modulators, etc.). Electronically adjustable properties of the device are involved in the design of an adjustable generator. The generator provides voltage- and current-mode square wave outputs that can be also used for differential square wave output when very simply modified. Application of the generator in simple pulse width modulator (PWM) is also introduced. A detailed analysis and Spice simulation results are given and main features of the circuits are compared to electronically controllable solutions of recent development in this field.