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

Synthesis of active inductors using SFG stamps

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.

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.

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.

The authors present a new architecture of a voltage-mode operational amplifier (VOA) which has been designed to provide high common-mode rejection ratio (CMRR) performance. The new amplifier attempts to retain the high slew-rate advantages of the current-feedback operational amplifier but within a balanced high input impedance structure, enabling it to be used as a conventional VOA. The amplifier is being developed as a high speed device operational amplifier. The key feature of the amplifier is an input stage with a similar dynamic response to the current-feedback operational amplifier. The new design is analyzed, and SPICE simulation results are presented. >

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.

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.

In this paper, a Negative Floating Fractional Order Capacitance Multiplier has been presented using a fractional order capacitor and Current Feedback Operational Amplifier (CFOA). The paper depicts the working of the proposed design through PSPICE simulations. Simulations of three instances of Negative Capacitor are presented. The proposed designs have been verified using a commercially available Current Feedback Op-amp macro model (IC AD-844A) and a fractional capacitance (FC) using RC Domino Ladder Network. The simulation results closely verify our theoretical propositions.

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.

-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.

A novel high DC accuracy and high CMRR performance current-feedback op amp (CFOA) is presented. The conventional architecture CFOA suffers from poor DC gain accuracy and CMRR due mainly to Early effects in the input stages. The new design is based on a bootstrapping technique applied to the input stage, and results in a CFOA with DC performance, CMRR and gain accuracy all substantially improved. All of these improvements are obtained without increase in circuit complexity and power consumption. Most of the other characteristics of the new CFOA are similar to those of a conventional design.

In this paper, a frequency analysis of a voltage feedback amplifier based on second generation current conveyors with inductive input/output impedance, is presented. The traditional voltage amplifier configured from voltage and current feedback operational amplifiers are studies and compared. PSPICE simulation confirms the theoretical approach.

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.