Design and implementation of grid multi-scroll chaotic circuit based on current feedback operational amplifier

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

ABSTRACTIn this paper, we present an exact analysis of finite gain inverting voltage amplifiers using current feedback operational amplifiers (CFOA) for use as stand-alone amplifiers or for being used in second-order active resistance capacitance (RC) filters such as Tow–Thomas biquads. The proposed circuits require one or two additional CFOAs/resistors/capacitors. The effect of finite output impedance at z terminal, input resistance at x terminal, and current mirror pole of the CFOA are studied. The circuits considered have been simulated using PSPICE using a behavioural macro-model of the CFOA as well as that of a practical CFOA AD 844.

-This paper presents the design of a sinusoidal, triangular, and square wave generator using a high speed current feedback operational amplifier (CFOA). A macro model for the CFOA is developed as well. The frequency of oscillation in all cases are derived and compared with the simulated values. The achieved frequency of oscillation for sinusoidal wave is 9.4 MHz to 15 MHz and the achieved frequency of oscillation for the triangular/rectangular wave is 6.75 MHz to 59.5 MHz. The advantage of using the current feedback operational amplifier is to get higher frequency of sinusoidal, triangular, and square wave.

Current feedback operational amplifiers: a tutorial In a didactic approach, the amplifying properties of an inverter stage using a current feedback operational amplifier (COA) and one using a voltage feedback operational amplifier (VOA) are compared. Then, following a discussion of COA modelling, the frequency and transient responses of a COA non-inverter stage are analysed.

A novel topology for realizing voltage-mode (VM) full-wave rectifier/sinusoidal frequency doubler based on current feedback operational amplifiers (CFOAs) and n-channel metal-oxide semiconductor (NMOS) transistors is proposed in this study. The proposed full-wave rectifier structure employs two CFOAs and three enhancement-mode NMOS transistors. With a slight modification, the sinusoidal frequency doubler circuit can be adopted from the full-wave rectifier circuit by replacing a grounded resistor instead of one of the NMOS transistors. Both of the proposed circuits enjoy low output and high input impedance properties which make them convenient for cascading easily with other VM circuits without needing any extra buffer circuits. No passive component matching conditions are needed. The proposed circuits are simulated by using SPICE program to verify the theoretical analysis.

In recent years, many articles came out where one could find the analysis of oscillatory systems of electric sinusoid signals generators with amplifiers called CFOA—current feedback operational amplifiers. As a rule, the analysis of such systems is made by applying mathematical modeling methods on the basis of the amplifier linear model, which does not allow estimating advantages and disadvantages of the systems realized with those amplifiers in comparison with classical systems. A nonlinear model of a current feedback operational amplifier (CFOA) is introduced in the paper; nonlinearity of “current mirror” is reflected in the form of current double limiting. The analysis of two known oscillatory systems has been carried out with the use of this non-linear model. Dependence between current limiting level, output voltage amplitude, and maximum oscillation frequency has been obtained. The paper shows that output current limiting under current output connection of capacitive load reduces frequency range and output voltage amplitude considerably and increases harmonic distortions in comparison with classical oscillatory systems. The research done has found that the application of new amplifiers does not give considerable advantages to the oscillatory systems with CFOA.

Mixed-mode chaotic circuit with Wien-bridge configuration: The results of experimental verification

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.

Synthesis of active inductors using SFG stamps

The current-feedback operational amplifier (CFA) is an active device which uses the supply-current sensing technique in order to achieve high performance features for analog signal processing applications. However, under certain load conditions, the CFA exhibits an unstable behavior. This work presents a new frequency model which rakes into account the non-unilateral characteristics of the CFA buffer stages and includes the load-dependent instabilities. The model can be easily incorporated into a standard macromodel for simulation purposes or used analytically for accurate circuit design based on CFAs. As a consequence of this approach, some improvements in the CFA structure could be suggested.

Low-voltage subthreshold CMOS current mode circuits: Design and applications

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.

In this paper, a circuit technique to extend the measuring range of a linear variable differential transformer (LVDT) is proposed. The transfer characteristic of the LVDT contains the odd function form of the cubic polynomial. Therefore, the measuring range of a commercial LVDT is linear in a narrow range compared to its physical dimensions. The wide measuring range of the LVDT requires a large structure of the LVDT, which increases the scale and the cost of the measurement system. The measuring range of the LVDT can be linearly extended to the maximum of the stroke range using the proposed technique. The realization of the proposed technique is based on the use of the hyperbolic sine (sinh) function of the electronic circuit building block, named the class AB bipolar amplifier. The class AB bipolar amplifier can be obtained by the current feedback operational amplifier (CFOA). The circuit of the proposed technique requires two CFOAs and an operational transconductance amplifier (OTA) as the active devices and all devices used in the proposed technique to synthesize the sinh function are commercially available. The proposed technique exhibits an ability to compensate for the nonlinear characteristic of the LVDT without digital components. The proposed technique is attractive in terms of its simple circuit configuration, small size, and low cost. The linear range extension of the LVDT used in this paper is significantly increased with a maximum error of about 18.3 μm of 6.2 mm at the full stroke range or the full-scale percentage error of about 0.295%. The results indicate that the proposed technique provides excellent performance to extend the measuring range of the LVDT without modifying the LVDT structure.

The design of low power and low voltage analog circuits is truly challenging. Therefore different approaches have been proposed and successfully employed. In this paper some of the low voltage topologies like Bulk Driven, Self-Cascode and DTMOS have been presented, and issues related to design are discussed briefly. These topologies are also used to design second generation current conveyors (CCII) and voltage mplifiers. The CCII is an important building block of a current feedback circuit like a current feedback operational amplifier (CFOA). Low voltage and low power are needed when those circuits are employed in the biomedical application and portable equipment. The designs are implemented using 0.18 µm CMOS technology.

In this paper a grounded negative inductor using single current differencing buffered amplifier (CDBA) is presented. The workability of the proposed inductance simulator is demonstrated through PSPICE simulations. Two instances of negative inductor were simulated. For simulation CDBA is realized using macro model of commercially available current feedback operational amplifier (CFOA) (IC AD844). The simulation results closely agree with the theoretical propositions.