Current Feedback Operational Amplifier Research Articles

Generalised approach for active‐RC quadrature oscillator circuit with grounded capacitors

This study introduces a new approach for realising a sinusoidal oscillator with three outputs, using an active-resistor-capacitor (RC) approach. Using the proposed approach, a new circuit employing three current feedback operational amplifiers and passive components is further introduced. The circuit employs two grounded capacitors and four resistors, out of which one is grounded. The new circuit based on the proposed generalised approach is relatively insensitive to the parasitic effects of active elements, and easy to design, by way of non-interaction of frequency and condition of oscillations. The proposed approach and the new proposed circuit provide three outputs, two of which are at low impedance nodes. The proposed generalised approach and the new circuit are verified through simulation and experimental results, using commercially available AD-844s integrated circuits and passive components. Thus, the work advances the existing knowledge on the active-RC oscillator design.

Improved current-mode wave active filter

ABSTRACT In this paper, a resistorless improved wave active filter (WAF) is presented using a comparatively new current-mode building block, namely extra X current-controlled current conveyor (EX-CCCII). The proposed wave active filter is designed in the current mode. The incident and reflected waves are used for designing the basic wave active elements, namely series and shunt inductors (L) and capacitors (C). The novelty of the circuit is that the mathematical operations like lossy integrator, unity gain amplifier, summation, and subtraction, required to realise the wave active elements, are accomplished by judiciously using the port relationships of EXCCCII. As a result of which the proposed circuit is compact and uses only two EXCCCIIs and one grounded capacitor for the realisation of wave elements (L and C). One 3rd and one 4th order Butterworth wave active filters are designed using EX-CCCII-based wave elements and simulated in cadence using 0.18 µm TSMC CMOS technology. The comparison indicates that the proposed WAF uses minimum numbers of analog building blocks (ABBs) and consumes the least power; moreover, the performances such as noise, percentage total harmonic distortion (%THD), and electronic controllability of cut-off frequency of the filters are also reported. Abbreviations: ABB: analog building block; FDNR: frequency-dependent negative resister; WAF: wave active filter; THD: total harmonic distortion; OTA: operational transconductance amplifier; CFOA: current feedback operational amplifier; VDTA: voltage differencing transconductance amplifier; OTRA: operational transresistance amplifier; CCDDCCTA: current-controlled differential difference current conveyor transconductance amplifier; DVCCCTA: differential voltage current-controlled conveyor transconductance amplifier; DVCCTA: differential voltage current conveyor transconductance amplifier; EX-CCCII: extra X current-controlled conveyor

A Novel Floating/Grounded Meminductor Emulator

Meminductor is a nonlinear two-terminal element with storage energy and memory ability. To date, meminductor element is not available commercially as memristor and memcapacitor are. Therefore, it is of great significance to implement a meminductor emulator for breadboard experiment. In this paper, a flux-controlled floating/grounded meminductor emulator without a memristor is presented. It is built with commercially available off-the-shelf electronic devices. It consists of single operational transconductance amplifier (OTA), single multiplier, two second-generation current conveyors (CCIIs), single current-feedback operational amplifier (CFOA) and single operational amplifier. Using OTA device introduces an additional control parameter besides frequency and amplitude values of applied voltage to control the area of pinched hysteresis loop of meminductor. Mathematical model of proposed emulator circuit is given to describe the behavior of meminductor circuit. The breadboard experiment is performed using CA3080, AD844, AD633J and LM741 for OTA, CCII–CFOA, multiplier and operational amplifier, respectively. Simulation and experimental test results are given to verify the theoretical analyses. Frequency-dependent pinched hysteresis loop is maintained up to 5 kHz. The presented meminductor emulator tends to work as ordinary inductor for higher frequencies.

Electronic Tuning Square-Wave Generators with Improved Linearity Using Operational Transresistance Amplifier

Two new electronic tuning current-mode square-wave generators are introduced in the ensuing paper. In the first proposed square-wave generator circuit, one Operational Trans-resistance Amplifier (OTRA) and two passive components are involved, along with two NMOS depletion mode transistors. This circuit generates a square-wave with almost equal and fixed duty cycles. The second proposed circuit is able to control both on-duty and off-duty cycles independently with the help of two passive components, two NMOS depletion mode transistors, and two diodes connected to the circuit. The frequency of the proposed circuits can be adjusted with the passive components connected to the circuit. Moreover, electronic tuning can also be achieved with the proposed circuits. The measured results that are included in the paper show the linear variation of a time period as compared with existing OTRA based square waveform generator. The performance of the proposed circuits is examined while using SPICE models. These circuits are built on a laboratory breadboard using commercially available Current Feedback Operational Amplifier (AD844 AN) and passive components are connected externally and tested for square waveform generation. The obtained results demonstrate good agreement with the theoretical values.

Comparative study of nature-inspired algorithms to design (1+α) and (2+α)-order filters using a frequency-domain approach

A precise control in the stopband attenuation characteristics can be achieved by using the fractional-step filters instead of the traditional integer-order filters. In this paper, nine nature-inspired optimization algorithms, such as five advanced variants of differential evolution (DE), three advanced variants of particle swarm optimization (PSO), and an efficient evolutionary strategy method (CMA-ES-RIS) are employed to design the fractional-step low pass Butterworth filter (FLBF). The proposed ( 1 + α ) and ( 2 + α ) order models, where α ∈ ( 0 , ​ 1 ) , are optimally approximated as an integer-order transfer function by using the magnitude-frequency information of the ideal FLBF. Comparisons regarding the solution quality and robustness reveal an improved accuracy for the DE variants and CMA-ES-RIS over all the PSO variants. Results from the pair-wise Wilcoxon rank-sum test demonstrate the superiority of enhanced fitness-adaptive differential evolution (EFADE) algorithm as the most efficient optimization tool for solving this problem. Comparisons with the state-of-the-art approaches also confirm the superior modelling accuracy of the proposed FLBFs. The canonical structure circuit realization of the FLBFs using current feedback operational amplifiers is presented. Simulations carried out in OrCAD PSPICE platform suggest proximity in the magnitude responses between the proposed and the theoretical models. The optimal design of stable, minimum-phase ( 2 + α ) order FLBFs is also presented for the first time without employing the cascading concept involving the integer-order Butterworth polynomials.

A Multifunctional Voltage Mode Fractional Order Filters using a Single CFOA

A multifunction voltage mode fractional order filter structure is described using a single current feedback operational amplifier (CFOA). This configuration realizes three fractional order filters (FOFs) namely fractional order low pass (FOLP), fractional order band pass (FOBP) and fractional order high pass (FOHP) filters. The performance of the proposed structure has been verified through PSPICE and MATLAB simulation results using macro model of AD844 type CFOA.

Optimal rational approximation of bandpass Butterworth filter with symmetric fractional-order roll-off

In this paper, a fractional-order bandpass Butterworth filter (FBPBF) exhibiting symmetric roll-off characteristic is approximated as an integer-order transfer function using a metaheuristic optimization approach. A novel cost function is proposed by considering the exact FBPBF magnitude characteristic obtained through cascading the (n+α), where n is an integer and 0<α<1, order lowpass and highpass Butterworth filter responses. Design examples considering various values of n and α are presented to illustrate the performance efficacy of the proposed approach. PSPICE simulations for the models realized using the current feedback operational amplifiers confirm proximity to the theoretical characteristics.

Synthetic Transformer Design Using Commercially Available Active Components

In this study, a novel synthetic transformer (ST), namely mutually coupled circuit, using commercially available active components such as current feedback operational amplifiers (CFOAs) is proposed. The proposed ST uses four CFOAs, two grounded capacitors and five resistors. It possesses only resistors but no capacitors attached in series to W/X terminals of the CFOAs; consequently, its high-frequency performance is well. Nevertheless, it needs a single matching condition for symmetrical coupling. As an application example, a double-tuned band-pass filter is given. The validity of the proposed circuit is demonstrated through several SPICE simulations and experiments.

CFOA-Based New Structure of Fractional Order Inverse Filters

This paper presents a CFOA-based fractional order inverse filter (FOIF) structure. Proposed structure utilizes two current feedback operational amplifiers (CFOAs), two fractional capacitors (FCs) and two resistors to design FOIFs to realize fractional order inverse low pass (FOILP), fractional order inverse high pass (FOIHP) and fractional order inverse band pass (FOIBP) responses. The proposed configuration of FOIFs is simulated in PSPICE using AD844 type CFOAs. Stability analysis and MATLAB simulations are also carried out to authenticate the theoretical propositions.

CMOS voltage and current feedback opamps: a comparison between two similar topologies

ABSTRACT The voltage feedback operational amplifier (VFOA) and the current feedback operational amplifier (CFOA) are the main voltage type output opamps currently used in electronics. The VFOA is a combination of an operational transconductance amplifier (OTA) used as an input stage and an output voltage buffer (VB). In this paper, the CFOA is described as a combination of an operational transconductance conveyor (OTC) used as an input stage and with an output voltage buffer. Two similar CMOS architectures are then defined, analysed and simulated in order to provide some elements of comparison. Results, from a typical CMOS 0.35μm transistor parameters, show the role of compensation capacitances in boosting the frequency performances of the non-inverting amplifier.

A Class of Single-CFOA-based Sinusoidal Oscillators

A class of second order sinusoidal oscillators is presented which employs a single Current feedback-operational amplifier, four capacitors and four to five resistors which can be realized by CMOS linear voltage controlled resistors (VCR). The proposed circuits are simultaneously single resistance controlled oscillators (SRCO) as well as single capacitor controlled oscillators (SCCO) providing independent control of condition of oscillation and frequency of oscillation through independent resistors as well as independent capacitors. To the best knowledge of the authors, any single-CFOA-based oscillators which are simultaneously SRCOs as well as SCCOs have not been reported in the literature earlier. SPICE simulation results using 0.18μm CMOS technology have been given which confirm the validity of the proposed circuits.

Optimal approximation of fractional‐order systems with model validation using CFOA

Optimal integer-order transfer function approximation of linear time-invariant fractional-order systems (FOS) using a straight-forward approach is proposed here. The error between the rational approximant and the FOS (commensurate/non-commensurate/oscillatory types etc.) is minimised directly in the frequency domain, subject to design stability constraints, by using the colliding bodies optimisation (CBO) algorithm. Comparisons with other well-known metaheuristics regarding the computational time and the design effort expended in parameter tuning justify the efficiency of the proposed method. The CBO-optimised models achieve a superior solution quality regarding both the magnitude and phase responses in comparison to the reported literature. Analogue circuit implementations of the models using the current feedback operational amplifier are also presented. Simulations carried out in OrCAD PSPICE environment validate the practical efficacy of the proposed models.

An active inductor employing a new four terminal floating nullor transconductance amplifier (FTFNTA)

ABSTRACTIn this scientific study, a new analog active building block named as four terminal floating nullor transconductance amplifier (FTFNTA) is implemented. The FTFNTA design offers a combined essence of both traditional four terminal floating nullor (FTFN) and an operational transconductance amplifier (OTA). The FTFNTA design is extended for the design of a lossless floating and grounded inductor simulator with few passive components. In addition, the performance and usefulness of the proposed inductor topology are also expanded for active filter applications: higher-order Butterworth high-pass filter and current mode multifunction filter. The functionality of the CMOS-based FTFNTA is integrated with a 0.18 µm Taiwan Semiconductor Manufacturing Company (TSMC) CMOS technology. Moreover, the FTFNTA is also realised using the current feedback operational amplifier (CFOA/AD844) and OTA (OTA/CA3080) of a commercially available IC to test the viability of the proposed inductor design. Finally, an application based on the inductor topology and its impedance characteristics are well analysed via PSPICE simulation.

ÜÇÜNCÜ DERECEDEN YENİ BİR QUADRATURE OSİLATÖR TASARIMI

Bu çalışmada, son zamanlarda oldukça fazla dikkat çeken bir aktif eleman olan Terslenmiş Akım Geri Beslemeli İşlemsel Yükselteç (ICFOA) kullanılarak üçüncü dereceden quadrature osilatör devresi sunulmuştur. Topoloji iki adet ICFOA, üç adet kapasitör ve üç adet direnç olmak üzere gerilim modlu ikinci dereceden alçak geçiren filtre ve gerilim modlu integratör yapısının kaskat bağlanıp kapalı çevrim oluşturması ile elde edilmiştir. Sunulan devrenin çalışabilirliği PSPICE benzetim programı ile denenmiş ve teorik sonuçlar ile örtüştüğü görülmüştür. Teorik kesim frekansı 3,979MHz ve benzetim sonucu ölçülen kesim frekansı ise 3,933MHz’dir. Benzetimde 0,35 μm MOSIS parametre seti ve ICFOA CMOS yapısı kullanılmıştır. Önerilen devrenin güç tüketimi 4,83mW’dır.

Revisiting the use of squared magnitude function for the optimal approximation of (1 + α)-order Butterworth filter

Optimal rational approximation of the fractional-order Butterworth filter (FBF) based on a two-step design procedure is proposed. Firstly, the coefficients of the squared magnitude function of an approximant which matches the squared magnitude response of the ideal (1 + α)-order FBF, where 0<α<1, are determined using the Genetic Algorithm (GA). Then, the stable model is used as an initial point for Powell’s conjugate direction algorithm (PCDA). The computational efficiency and the robustness of the suggested strategy are justified using illustrative examples. The proposed designs show a marked improvement in solution quality compared to the state-of-the-art. PSPICE responses for the FBFs realized using current feedback operational amplifiers (CFOA) confirm a close match with the theoretical characteristic. Python code for implementing the proposed designs using the Powell’s method is also provided.

Dual Output Sinusoidal Oscillator Using Second Generation Current Controlled Conveyor

Second Generation Current Controlled Conveyor (CCCII) based tunable Dual Output Sinusoidal Oscillator (MSO) is proposed. It consists of three CCCIIs, a resistor and two grounded capacitors. By tuning external DC bias current, the oscillator frequency and commencement of its oscillations are controlled electronically. The proposed circuit is verified using PSPICE simulator and also on laboratory breadboard using commercially available integrated circuits Current Feedback Operational Amplifier (AD844AN) and Operational Transconductance Amplifier (LM13600) at a supply rail voltage of ±6 V. Further its nonlinearities, sensitivities, performance characteristics are also verified. Comparison of the proposed topology with the ongoing methods are also undertaken. PSPICE simulation results are verified with a low supply voltage of ±1 V, temperature analysis, analysis by using Montecarlo method and finally Total Harmonic Distortion (THD) is also demonstrated.

CFOA based a new grounded inductor simulator and its applications

A new grounded inductor simulator (GIS) with the property of improved low frequency performance is proposed in this paper. The proposed GIS includes two current feedback operational amplifiers, three resistors and a grounded capacitor. As applications for the proposed GIS, a second-order very high-Q band-pass filter (BPF) and a quadrature oscillator (QO) are given. The very high-Q BPF and the QO have low total harmonic distortion values. Nevertheless, for proper operation, the proposed GIS, the very high-Q BPF and the QO need a single resistive matching constraint. Many SPICE simulations and an experiment for the very high-Q BPF are achieved.

A CFOA-Based Voltage-Mode Multifunction Biquadratic Filter and a Quadrature Oscillator Using the CFOA-Based Biquadratic Filter

This paper proposes a new high-input impedance current feedback operational amplifier (CFOA)- based voltage-mode multifunction biquadratic filter and a voltage-mode quadrature oscillator using the proposed high-input impedance CFOA-based biquadratic filter. The proposed high-input impedance CFOA-based voltage-mode multifunction biquadratic filter uses three CFOAs, three resistors, and two grounded capacitors with two inputs and three outputs. The filter can simultaneously realize non-inverting low-pass, non-inverting band-pass, and non-inverting band-reject filtering functions at the high-input impedance terminal while the inverting band-pass and non-inverting high-pass filtering functions can also be obtained by applying another high-input impedance terminal. The filter offers orthogonal control of resonance angular frequency and quality factor. The proposed high-input impedance CFOA-based voltage-mode multifunction biquadratic filter can be used to implement a voltage-mode quadrature oscillator with an independently controlled the frequency of oscillator and the condition of oscillation. The OrCAD PSpice simulation and experimental results of the commercially available integrated circuit, AD844AN, are used to confirm the characteristics of the proposed filter and oscillator.

New simple chaotic and hyperchaotic system with an unstable node

This article presents a new chaotic and hyperchaotic oscillator with a sine-hyperbolic nonlinearity term. The proposed 3D chaotic system generates chaotic flow within an unstable node equilibrium. In addition, an extension of the proposed chaotic circuit produces 4D hyperchaotic nature by including an external capacitor in the basic design. This hyperchaotic system generates chaotic flow with the line of equilibrium which has an unstable null equilibrium termed as a special case of multi-stability. The chaotic behavior of the proposed system is obtained by using essential dynamical properties and its practical feasibility can be demonstrated through Current Feedback Operational Amplifier (CFOA) with traditional electronic components. The proposed chaotic and hyperchaotic system have some important features namely simple model without multiplication terms, simple circuitry, multi-stability, minimum component count and sensitive with passive components that signifies the advantages for the signal processing circuit and its applications. On the other hand, various bifurcation sequences along with its typical time series chaotic responses are well observed through simulation and experimental verification that validates the proposed chaotic oscillator theory.

A tuneable active inductor employing DXCCTA: Grounded and floating operation

An active inductor employing both grounded as well as floating mode using Dual-X Current conveyor Transconductance Amplifier (DXCCTA) is presented in this article. The novelty of the proposed inductor topology is to exhibit simultaneously both positive and negative inductor characteristics without any change in the topology. In addition, active realization of positive and negative fractional order inductor are also presented. The performance characteristics of the proposed inductor models are verified using CMOS as well as Current Feedback Operational Amplifier (CFOA/IC AD844) based DXCCTA block. The compatibility of the proposed inductors is suitable for various application viz. active filter design using positive inductor and inductance cancellation using negative inductor. The theoretical explanations of the proposed designs are well verified through PSPICE simulations and experimental platform.