Current-mode Operational Amplifier Research Articles

Design of a fully differential current mode operational amplifier with improved input–output impedances and its filter applications

In this paper, a CMOS implementation of a fully differential current-mode operational amplifier (COA) is presented. To achieve very low input resistance, a new technique based on a positive feedback is used in the input transimpedance stage. Additionally, traditional current output stage (Arbel Goldminz output stage) with improved output resistance is selected as a transconductance stage. Results of simulations exhibit 96 dB DC gain, nearly 120 Ω input, 30 M Ω output resistances and a gain-bandwidth product exceeding 90 MHz. The proposed COA is operated under ± 1.5 V voltage supplies and designed with 0.35 - μ m CMOS process. Furthermore, COA-based fourth-order band-pass (BP) filter consisting of Butterworth low-pass (LP) and high-pass (HP) filters is realized as an application example. SPICE simulation results are included to verify correctness of the designs.

Design and analysis of low-voltage current mode operational amplifier with differential-input and differential-output

In this work, a new CMOS current operational amplifier (COA) with fully differential input and differential output is proposed and analysed. The amplifier is implemented from a differential current mirror input transimpedance stage followed by a differential output transconductance gain stage. A differential mode design technique is proposed and used in the feedback circuit. This configuration is the current mode counterpart of the traditional voltage operational amplifier (VOA). The simulation results of the new COA are based upon the 0.5μm CMOS process and ±1.5V supply voltage. The new COA exhibits an open-loop differential gain of 51.71dB with the gain-bandwidth product 314MHz and a settling time of 14ns. The design and optimization guidelines of the new COA have been developed and analysed so that they can be applied to the design of high-performance COA.

A synthesis of a novel current-mode operational amplifier

In this letter, a novel current-mode operational amplifier (COA) is proposed. The proposed COA can operate at 2 V (±1 V) supply voltage. For high frequency operation it has only an npn transistor in signal path. Finally, SPICE simulation are shown to verify the performance of the proposed COA.

High-performance complementary metal-oxide-superconductor field effect transistor (CMOSuFET) current-mode operational amplifier

A high-performance CMOSuFET current-mode operational amplifier is introduced using a MOSuFET, with P type NCCO (normal conducting copper oxide) as substrate, P type HTCOSu (high-temperature copper oxide superconductor) as drain and source electrodes and formed through the proximity effect. We study the operation and characteristics of the superconducting operational amplifier. It shows high current gain and wide band, is significantly less power hungry than a semiconductor CMOSFET operational amplifier and has the possibility of acting as a high-performance building block of the current-mode analogue VLSI (very-large-scale integrated) inside a discrete time or continuous time signal processing system.

A CMOS current-mode operational amplifier

A fully differential-input, differential-output, current-mode operational amplifier (COA) is described. The amplifier utilizes three second-generation current conveyors (CCIIs) as the basic building blocks. It can be configured to provide either a constant gain-bandwidth product in a fully balanced current-mode feedback amplifier or a constant bandwidth in a transimpedance feedback amplifier. The amplifier is found to have a gain-bandwidth product of 3 MHz, an offset current of 0.8 mu A (signal range +or-700 mu A), and a (theoretically) unlimited slew rate. The amplifier is realized in a standard CMOS 2.4- mu m process.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A differential-input, differential-output current mode operational amplifier

Abstract A current operational amplifier with differential input and differential output is described. The amplifier is based on the parallel connection of a CCII+ current conveyor and a CCII− current conveyor followed by a differential output transconductance gain stage. The performance of the amplifier is analysed and experimental results obtained from an implementation using standard operational amplifiers and current mirrors realized using transistor arrays are presented and compared to the theoretical analysis. It is concluded that the static small signal open loop gain and the frequency response matches the performance of conventional voltage operational amplifiers. The input offset and bias errors and the common mode rejection are shown to be strongly dependent on the matching accuracy of the current mirrors used in the conveyors. The proposed configuration can easily be integrated into a monolithic amplifier in either CMOS or bipolar technology.

Constant-bandwidth current mode operational amplifier

A current mode operational amplifier with a low impedance output for feedback connection is proposed and analysed theoretically. It is found to have a constant bandwidth independent of the gain in a closed loop configuration. This property is due to the loop gain independent of the closed loop gain. The amplifier is shown to be composed of a current conveyor input stage and another current conveyor output stage. Experimental results are presented to verify the constant bandwidth performance, and it is concluded that the proposed configuration is suitable for high frequency current mode amplifiers.

Differential current input cell with common mode feedback

A bipolar fully-differential current cell which employs a novel common mode feedback technique to achieve DC stability and a good rejection of common mode signals is described. These properties make the cell extremely suitable for use as the differential input stage to a current mode operational amplifier, as well as finding application in numerous other current mode circuits and systems.

Novel bipolar differential input/output current-controlled current source

A new bipolar differential input/output current-controlled current source (CCCS) is described. The basic cell consists of a translinear array of six transistors with two bipolar inputs, and is suited for the input stage of a differential current-mode operational amplifier.