New CFOA-based floating immittance emulators

This paper presents four new topologies for emulating floating immittance functions. Each circuit uses two or three current-feedback operational-amplifiers (CFOAs) and three passive elements. The proposed topologies can emulate positive/negative lossless and lossy floating inductances, and positive/negative capacitance, resistance and inductance multipliers in addition to floating frequency-dependent positive and negative resistances. The functionality of the proposed circuits is verified using the Advanced Design System software and the AD844 CFOA. The simulation results are in excellent agreement with the theoretical calculations.     

New lossy/loss-less synthetic floating inductance configuration realized with only two CFOAs

A new CFOA-based lossy/loss-less floating inductance circuit is introduced which, in contrast to previously known configuration requiring three to four CFOAs, employs only two CFOAs along with only five passive components. The workability of the new FI circuit has been demonstrated by using it to design a second order notch filter and a fourth order Butterworth low pass filter by realizing the circuit using commercially available AD844-type CFOAs.     

Positive/negative lossy/lossless grounded inductance simulators employing single VDCC and only two passive elements

Actively simulated grounded inductors have been used in several applications ranging from filter to oscillator design as well as cancellation of parasitic inductances. In this paper, new grounded inductance simulators employing only one voltage differencing current conveyor (VDCC) and two passive components are proposed. Two new topologies for realizing positive and negative lossless inductances and four different topologies for realizing lossy inductances are proposed. The aim of this paper is to present new inductance simulators using the minimum number of active and passive components. The proposed inductance simulators can be tuned electronically by changing the biasing current of the VDCC. Moreover, the circuits do not require any conditions of component matching. Finally, using one of the proposed inductance simulators a third-order high-pass filter is constructed. The performance of the proposed filter is verified and simulated by using SPICE.     

Realizations of Grounded Negative Capacitance Using CFOAs

The paper presents new realizations of grounded negative capacitance, using current feedback operational amplifiers (CFOAs), two resistors and one capacitor. All the proposed realizations are canonic in the number of passive components and do not require any critical component matching condition. Application examples in capacitive cancellation schemes and resistance-controlled low-frequency quadrature sinusoidal oscillator design are provided. The workability of the circuits has been verified by PSPICE simulations.     

Applications of the current feedback operational amplifiers

The current feedback operational amplifiers (CFOAs) are receiving increasing attention as basic building blocks in analog circuit design. This paper gives an overview of the applications of the CFOAs, in particular several new circuits employing the CFOA as the active element are given. These circuits include differential voltage amplifiers, differential integrators, nonideal and ideal inductors, frequency dependent negative resistors and filters. The advantages of using the CFOAs in realizing low sensitivity universal filters with grounded elements will be demonstrated by several new circuits suitable for VLSI implementation. PSPICE simulations using the AD844-CFOA which indicate the frequency limitations of some of the proposed circuits are included.     

New two CFOA-based sinusoidal RC oscillators with buffered outlet

Using a unified representation for a class of buffered-outlet two current-feedback operational amplifier (CFOAs)-based sinusoidal oscillators, new circuits of this type can be systematically discovered. A catalogue of four circuit structures, each structure realizing nine oscillator circuits, is presented. Moreover, using the RC:CR transformation, additional nine oscillator circuits can be obtained from each structure. While each circuit requires five passive elements, some of the circuits enjoy one or more of the following attractive features: use of grounded capacitors, feasibility of absorbing the parasitic components of the CFOAs and orthogonal tuning of the frequency and the startup condition of oscillation.     

New CFOA-based sinusoidal oscillators retaining independent control of oscillation frequency even under the influence of parasitic impedances

There have been two efforts earlier on evolving CFOA-based fully-uncoupled oscillators i.e. circuits in which none of the resistors controlling the frequency of oscillation (FO) appear in the condition of oscillation and vice versa. However, a non-ideal analysis of the earlier known circuits reveals that due to the effect of the parasitic impedances of the CFOAs, the independent controllability of FO is completely destroyed. The main objective of this paper is to present two new fully-uncoupled oscillators in which the independent controllability of the FO remains intact even under the influence of the non-ideal parameters/parasitics of the CFOAs employed. The workability of the proposed circuits has been confirmed by experimental results using AD844-type CFOAs.     

Multiple Input Single Output Universal Biquad Filter with Current Feedback Operational Amplifiers

A novel Multiple Input Single Output (MISO) universal biquad filter topology realized using Current Feedback Operational Amplifiers (CFOAs) is introduced in this paper. With regards to the corresponding already published MISO universal biquads with CFOAs, the proposed topology simultaneously offers the benefits of employing only grounded capacitors, absence of any imposed constraint related to the values of input signals, and orthogonal adjustment between the quality factor and resonant frequency of the filter. The operation of the proposed biquad has been verified through experimental results by utilizing the commercially available AD844 CFOA discrete component.     

On the Realization of Universal Current Mode Biquads Using a Single CFOA

The four terminal Current feedback op-amps (CFOA) with an external compensation pin, such as AD844, have received prominent attention during the past decade as alternative building blocks for analog circuit design because of their significant advantages over the traditional voltage-mode op-amp (VOA). A popular application of CFOAs has been in realizing voltage-mode (VM) and current-mode (CM) biquad filters. Previously known universal CM biquads (i.e. those capable of realizing all the five generic filter functions namely, low-pass, band-pass, high-pass, notch and all-pass) realizable with CFOAs require two to nine CFOAs. Although a few dual-function/three-function single-CFOA-based CM circuits have appeared in literature, no single-CFOA-based canonic universal CM biquad with explicit CM output has been reported in the literature up until now. This paper fills this void by presenting a set of eight minimal universal CM biquads all of which are realizable with only a single CFOA. The non-ideal analysis of the proposed circuits has been presented, their comparative features, advantages and limitations have been brought out. The workability of all the proposed circuits has been confirmed by PSPICE simulations and experimental results based upon AD844 type CFOAs.     

A new approach for the realization of voltage-mode second-order universal filters using current conveyors

In this work two different types of topologies are derived for realization any second-order filter characteristic by choosing properly, the admittances of passive elements. These topologies use two second-generation current conveyors (CCIIs). One of the topologies involves different types of CCIIs whereas the other uses the same type of CCIIs together with a unity gain voltage buffer. The buffer used provides not only low output impedance but also facilitates cascading of the filter circuits thus obtained. It is possible to derive many different filters realizing any second-order transfer function by the use of the proposed topologies. Moreover, the produced filters have low-sensitivity performance and permit orthogonal controlling of both the quality factor and the natural angular frequency.     

On the Realization of Simulated Inductors with Reduced Parasitic Impedance Effects

In this paper, a method for reducing the parasitic impedance effects of the current feedback operational amplifiers (CFOAs) in an inductor simulator at low frequencies is proposed. Also, two novel grounded inductors employing a current follower (CF) and a second generation current conveyor (CCII) are given to illustrate the parasitic reduction technique clearly. The low frequency restrictions of the proposed inductors due to terminal parasitic resistances can be improved by using the presented parasitic impedance reduction technique. SPICE simulations show that the presented inductor employing CFOAs in a voltage-mode (VM) band-pass and high-pass filter application has lower parasitic effects at low frequencies. In addition to simulation results, experimental test results are given to verify the theory.     

Universal current mode biquad using a single CFOA

Because of their several advantages over the traditional voltage mode op-amp, current feedback op-amps (CFOAs) have attracted prominent attention as alternative building blocks for biquad filter realization. Previously known universal current mode (CM) biquads (i.e. those capable of realizing all five generic filter functions, namely low-pass, band-pass, high-pass, notch and all-pass) are realizable with CFOAs but require two to nine CFOAs. Although a few dual-function/three-function single-CFOA-based CM circuits have appeared in the literature, no single-CFOA-based canonic universal CM biquad with explicit CM output has been reported until now. This paper presents such a circuit. The workability of the proposed circuit has been confirmed by PSPICE simulations based upon AD844-type CFOAs.     

Wide-bandwidth CFOA with high CMRR performance

In this paper the authors analyze the conventional current-feedback operational amplifier (CFOA) in terms of common-mode-rejection ratio (CMRR) performance, and having identified the mechanism primarily responsible for the CMRR, they propose two new architecture CFOAs. These new CFOAs are further developed, and modified to provide improved bandwidth, AC gain accuracy and high CMRR performance. The key features of the two proposed new CFOAs are the designs of the internal voltage followers which have two separate biasing currents with a similar dynamic architecture to that of the conventional CFOA. The magnitude of one bias current determines the value of the maximum CMRR, and the second can be used to maximize bandwidth.     

New grounded immittance function simulators using single current feedback operational amplifier

Using unified representations for single current-feedback operational amplifier based immittance function simulators, new circuits can be systematically discovered. In this article a catalogue of three generic circuit structures is presented. The first structure uses three passive elements to realize either two different grounded lossless negative inductances or two different lossless grounded frequency-dependent positive resistances, and uses four passive elements to realize two different grounded series connected negative resistance and negative inductance. The second structure uses three passive elements to realize a grounded lossless negative inductance and four passive elements to realize either a grounded series connected negative capacitance and a positive resistance or a grounded positive (or negative) series connected inductance and a positive resistance. The third structure uses three passive elements to realize either a grounded negative inductance in series with a negative resistance or a grounded negative capacitance divider in addition to the classical grounded negative impedance converter. Moreover, some of the previously reported immittance function realizations can be systematically obtained from the proposed generic structures.     

A dual-path bandwidth extension amplifier topology with dual-loop parallel compensation

A dual-path amplifier topology with dual-loop parallel compensation technique is proposed for low-power three-stage amplifiers. By using two parallel high-speed paths for high-frequency signal propagation, there is no passive capacitive feedback network loaded at the amplifier output. Both the bandwidth and slew rate are thus significantly improved. Implemented in a 0.6-/spl mu/m CMOS process, the proposed three-stage amplifier has over 100-dB gain, 7-MHz gain-bandwidth product, and 3.3-V//spl mu/s average slew rate while only dissipating 330 /spl mu/W at 1.5 V, when driving a 25-k/spl Omega///120-pF load. The proposed amplifier achieves at least two times improvement in bandwidth-to-power and slew-rate-to-power efficiencies than all other reported multistage amplifiers using different compensation topologies.     

Improved realization of canonical Chua's circuit with synthetic inductor using current feedback operational amplifiers

In this paper, we report an improved implementation of an inductorless third order autonomous canonical Chua's circuit. The active elements as well as the synthetic inductor employed in this circuit are designed using current feedback operational amplifiers (CFOAs). The reason for employing CFOAs is that they have better features such as high slew rate and high speed of operation, which enable the circuit to operate at higher frequency ranges, when compared to the circuits designed using voltage operational amplifiers. In addition to this, the inclusion of CFOAs provides a buffered output which directly represent a state variable of the system. The Multisim simulations in the time and frequency domains confirm the theoretical estimates of the performance of the proposed circuit at high frequencies. It is also confirmed through hardware experiments.     

On Current Feedback Operational Amplifier-Based Realization of Chua's Circuit

Because they offer some significant advantages over conventional operational amplifiers, current feedback operational amplifiers (CFOAs) have been used instead of voltage operational amplifiers (VOAs) in new implementations of the chaotic Chua’s circuit. In this study, after giving a comparative investigation of CFOA-based realizations of Chua’s circuit, we will present an alternative CFOA-based realization of Chua’s circuit combining the CFOA-based circuit topologies proposed for nonlinear resistor and inductor elements in the literature. This realization offers an alternative solution for readers studying Chua’s circuit and high-frequency chaotic oscillations. The PSpice simulation experiments performed in both the time and frequency domains confirm that the proposed circuit can generate the original chaotic oscillations of Chua’s circuit and that it exhibits excellent performance at high frequencies.     

Floating Immittance Function Simulator and Its Applications

A new floating immittance function simulator circuit is proposed using two different active elements, a dual-output second generation current conveyor (DO-CCII) and an operational transconductance amplifier (OTA). The presented circuit can realize a positive and negative floating inductor, capacitor and resistor depending on the passive component selection. Since the passive elements are all grounded, this circuit is suitable for fully integrated circuit design. The circuit does not require any component matching conditions, and it has a good sensitivity performance with respect to tracking errors. Moreover, the proposed positive and negative inductance, capacitor and resistor simulator can be tuned electronically by changing the biasing current of the OTA or can be controlled through the grounded resistor or capacitor. The proposed floating inductor simulator circuit is demonstrated by using a SPICE simulation for 0.35 μm TSMC CMOS technology. The proposed circuit consumes an average power of 1 mW using ±1.5 V supply voltages.     

Novel grounded parallel inductance simulators realization using a minimum number of active and passive components

In this paper novel lossless and lossy grounded parallel inductance simulators are reported. All grounded inductor simulator circuits employing only a single DXCCII and three passive components are proposed. The proposed topologies realized all grounded parallel inductance variations. To demonstrate the performance of the presented DXCCII based parallel inductance simulators, we used one of the circuits to construct a third order high-pass filter, a voltage-mode band-pass filter and LC oscillator. Simulation results are given to confirm the theoretical analysis. The proposed DXCCII and its applications are simulated using CMOS 0.35 μm technology.