Design of Sinusoidal, Triangular, and Square wave Generator Using Current Feedback Operational Amplifier (CFOA)

Electro-coalescence of two charged droplets under pulsed direct current electric fields with various waveforms: A molecular dynamics study

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 introduces a new simple Schmitt trigger circuit using a plus-type differential voltage-current conveyor (DVCC+) and only two grounded resistors. The proposed circuit is very simple and enjoys adjustable lower and higher threshold voltages as well as the output saturation levels. The application of the proposed Schmitt trigger circuit to the square/triangular wave generator is also given. Moreover, a current feedback operational amplifier (CFOA)-based square/triangular wave generator is derived from the proposed DVCC+-based circuit. Simulation and experimental results are presented to exhibit the performance of the proposed circuits.

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.

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

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.

Synthesis of active inductors using SFG stamps

In this paper, a method is proposed to realize the grid multi-scroll chaotic system with the current feedback operational amplifier (CFOA). Firstly, nonlinear circuit is designed based on the CFOA. Then the grid multi-scroll chaotic circuit is designed and relevant circuit parameters are calculated. Finally circuit simulation is conducted, and the results show that the circuit has a higher central frequency, needs less components, and possesses simpler circuit structure, good frequency characteristic and port characteristic of the CFOA.

The realization of two integrator loop oscillators using Operational Amplifiers (Op Amps) is reviewed and a new additional circuit to provide independent control on the oscillation condition is proposed. Four new grounded capacitor oscillator circuits using unity gain cells and having independent control on the condition of oscillation and on the frequency of oscillation are introduced. The link between the Op Amp based two integrator loop oscillators and three Current Feedback Operational Amplifier (CFOA) based oscillators is detected and clearly explained. This paper serves also as a tutorial paper in introducing the subject of second order two integrator loop oscillators using state variable matrix equation and Nodal Admittance Matrix (NAM) equation.

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.

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.

Two novel topologies of lossless grounded negative inductance simulator configuration using only one Current Differencing Buffered Amplifier (CDBA) and five passive elements are introduced in this paper. The value of the simulated inductances can be independently controlled without disturbing the condition of realization of inductance, that provides the non-interactive control. The properties of the proposed circuits are validated using PSPICE simulation. The value of the inductance simulator has also been achieved experimentally using commercially accessible Current Feedback Operational Amplifier (CFOA)-based IC AD844AN and found to agree well with the theoretical hypotheses.

MOS-C realizations of the Kerwin–Huelsman–Newcomb (KHN) circuit using the commercially available Voltage Operational Amplifier (VOA) and the Current Feedback Operational Amplifier (CFOA) are reviewed in this paper. Additional MOS-C KHN realizations using the Operational Transresistance Amplifier (OTRA) and the Differential Current Voltage Conveyor (DCVC) are also included. MOS-C realizations of the KHN circuit using CMOS operational amplifier, CMOS current feedback operational amplifier and CMOS operational transresistance amplifier are also given.Spice simulation results using 0.18 CMOS technology model from MOSIS are included together with detailed comparison tables to demonstrate the differences between MOS-C KHN circuits using both of the commercially available active building blocks and CMOS integrated building blocks. A comparison with the Gm-C KHN circuit is also included.

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