Current Feedback Op-amps Research Articles

Synthesis of single-resistance-controlled oscillators using CFOAs: simple state-variable approach

A simple state-variable synthesis approach has been presented which makes it possible to evolve current feedback op-amp (CFOA)-based single-resistance-controlled oscillators (SRCO) systematically. Synthesised SRCOs possess several novel features and their workability has been confirmed experimentally as well as through SPICE simulations using commercially available AD844 CFOAs.

A theoretical study of the stability of high frequency current feedback op-amp integrators

In this paper, we present a comprehensive theoretical study of the stability of current feedback op-amps, when used with both resistive and capacitive feedback. The paper identifies some of the more subtle features of designing with current feedback op-amps, and the impact these features have on the amplifiers stability. There is a common misconception that the current feedback op-amp will oscillate when connected as a classical active R-C integrator; in this paper we prove that this is not necessarily the case and theoretically demonstrate that under certain design conditions the current feedback op-amp has in fact enormous potential for high frequency integrator design. Theoretical analysis is confirmed by both simulation and measured results using commercially available current feedback op-amps, and comparisons are made with classical voltage-mode op-amps.

Current-feedback opamp suitable for CMOS VLSI technology

A CMOS current feedback opamp, suitable for VLSI technology, is presented. The design is based on a new voltage buffer topology with low output impedance achieved by using local current feedback. Simulation results show low power dissipation, wide bandwidth and very good linearity.

A unitary analysis of voltage mode and current feedback op-amp circuits

This paper presents a unitary analysis method for voltage mode (VM) and transimpedance-current feedback (CFB) op-amp circuits. This methods uses a unified model for both op-amps; thus it permits a direct comparison for the circuit parameters. The point of the presented method is the separation of the signal graph of the analyzed circuit in two different paths: one that controls the gain and another that determines the circuit bandwidth. Thus one obtains a direct sight on the circuit elements that control this parameters. We extend the analysis method on differential current feedback (DCFB) op-amps circuits. Symbols for CFB and DCFB were introduced to simplify the circuit descriptions. As an application we analyze some high precision and large bandwidth amplifiers.

A dual current feedback op amp in CMOS technology

A CMOS circuit configuration implementing a current feedback or transimpedance op amp (CFB op amp) is presented. The architecture of the circuit is derived from similar bipolar CFB op amps. The properties of the CMOS implementation are similar to those of its bipolar counterparts, i.e., a high slew rate and a bandwidth which is independent of the closed-loop gain when the op amp is used with current feedback. Further, it is shown how two CFB op amps can be connected to achieve a non-slew-rate-limited voltage-mode op amp.

Wideband and high gain current-feedback opamp

A technique to improve the maximum gain-bandwidth product of the current-feedback opamp is described. Simulated results using high speed complementary bipolar transistors demonstrate that closed-loop voltage gains of 100 can be achieved with maximum bandwidths of 100 MHz with slew rates of the order of 1000 V/μS.

High speed, current conveyor based voltage mode operational amplifier

A voltage mode operational amplifier (opamp) built from two current conveyors is proposed as an approach to an opamp featuring a high slew rate. The suggested configuration has the slew rate characteristics of commonly available transimpedance amplifiers but provides two high impedance (voltage mode) inputs similar to conventional opamps. The configuration has been verified experimentally by using a dual current feedback opamp in a noninverting amplifier connection. From the measured results it is concluded that the proposed configuration is suited for the implementation of high speed integrated opamps in either bipolar or CMOS technology.