High CMRR current-feedback operational amplifier

Despite excellent high frequency and high speed performance, current-feedback operational amplifiers (CFOAs) generally exhibit poor common-mode rejection properties, which limits their utility. In this paper the authors analyse the conventional (CFOA) in terms of common-mode rejection ratio (CMRR) performance, and, having identified the mechanism primarily responsible for the CMRR, they present a modified CFOA input stage circuit design by introducing a combination of a bootstrapping technique and folded cascode transistors. Simulation results of this new CFOA architecture indicate that the amplifier has significantly improved both CMRR and gain accuracy. Other key characteristics are also improved, with the notable exception of slew rate, which is reduced as a consequence of the new topology.     

New current-feedback amplifier configuration

Current-feedback amplifiers are increasingly being used, particularly because of their near gain-independent bandwidth property, but the variety of current-feedback amplifiers is somewhat limited. This paper describes a new current-feedback amplifier configuration that utilizes a voltage amplifier in conjunction with a current conveyor in an unconventional manner, and is particularly suited for low-voltage CMOS implementation. A complete analysis is given, and experimental results using a variety of commercial devices confirm the validity of the proposed design.     

一种低噪声高共模抑制比运算放大器的分析与设计

低噪声高共模抑制比的运算放大器是将套筒式共源共栅结构、差分输出和共模负反馈相结合,设计出的一种新型运算放大器.基于SMIC0.18 μm工艺模型对电路进行设计,仿真结果表明该电路的开环增益为82.3 dB,相位裕度为66°,共模抑制比为122 dB,增益平坦带宽为15 MHz,噪声为7.781 nV/sqrt （Hz）,达到设计要求.     

A nonlinear macromodel for current-feedback operational amplifiers

This paper proposes a macromodel to emulate the nonlinear behavior of current-feedback operational amplifiers (CFOAs) at low-frequency. The main difference between this macromodel and those reported previously in the literature is that herein, real physical active device performance parameters along with parasitic elements associated to the input–output terminals of the amplifier are considered. To validate the deduced behavioral model, a saturated nonlinear function series (SNFS) based on CFOAs is built and numerical simulations are generated. In this point, the modeling problem is cast in terms of an augmented set of equations but that, unlike a piece-wise linear (PWL) approach, the dynamic behavior of each CFOA is considered. Afterwards, the SNFS is experimentally tested by using commercially available active devices, confirming good agreement among theoretical simulations and experimental tests at two operating frequencies and showing a better accuracy compared with a PWL approach and a linear model for CFOAs. Because the derived nonlinear macromodel for CFOAs is used for generating the behavioral model of the SNFS, one concludes that the latter is also both accurate and efficient with respect to traditional techniques, such as PWL approaches.     

Dual-input single-tunable integrators and differentiators using current-feedback amplifier

Some new active-RC integrator and differentiator circuits using the currentfeedback amplifier (CFA) device are proposed; both current-mode and voltagemode versions are reported. The novelties of the designs are dual-input differential capability, single-resistor tunability at low sensitivities and realizability of the pole/zero at the origin. Experimental results are included.     

Open-loop output characteristics of a current feedback operational amplifier

The output characteristics of the basic current feedback operational amplifier (CFOA) in the linear region, on open-loop, would not appear to have been treated in the literature. This is possibly because it is not straightforward to determine, the problem being that the output saturates without the closed-loop connection. This paper considers a theoretical discussion that explains the results of simulation.     

集成运算放大器的特性及应用

集成运算放大器是放大电路中非常重要的元器件,可靠性高,使用方便,随着技术指标的不断提高,它可当作理想器件来处理.不会造成不可允许的误差。在学习时应熟练掌握它的线性与非线性特性以及其在信号的运算、处理和电路的比较分析等方面的相关应用。     

Analysis of the settling behavior of an operational amplifier

The settling behavior of a pole-splitting compensated operational amplifier is analyzed using a second-order (two-pole) transfer function. It is shown that although the slewing period of the amplifier is well approximated by the commonly used formula for slew rate, the settling behavior after the slewing period can only be fully explained using a second-order transfer function. Simple criteria relating the circuit parameters to the damping ratio of a second-order feedback system are given. Analytical expressions for the amplifier responses and settling times are derived. The analysis is justified by close correspondence with computer simulations.     

Current-mode and voltage-mode universal biquads using a single current-feedback amplifier

A new current-mode universal biquad and a new voltage-mode universal biquad using a single current-feedback amplifier are proposed in this paper. Both biquads enjoy the following advantages: realization of highpass, bandpass and lowpass filtering from each configuration, avoidance of input voltage tracking error in a current-feedback amplilfier; only one active component; no requirement for match components; low passive and active sensitivities. An inverting amplifier is used to form a notch filter. Experimental results are obtained to prove the theoretical analyses.     

MOS-C single amplifier biquads using the operational transresistance amplifier

A configuration for the realization of voltage-mode second-order filters employing a single operational transresistance amplifier (OTRA) as the active element is presented. This topology can synthesize lowpass, highpass, bandpass, notch and allpass filtering functions. The presented filters are suitable for MOS-C implementation, yielding the filter parameters to be electronically tunable. Theoretical analysis is verified with PSPICE simulation.     

Low noise characteristics of a GaAs-AlGaAs multiple-quantum-wellsemiconductor laser amplifier

Low noise characteristics are experimentally demonstrated in a multiple-quantum-well laser amplifier. The measured noise figure of a GaAs-AlGaAs traveling-wave laser amplifier at a 20 dB signal gain was found to be 4.6 dB. This is the smallest value reported for semiconductor laser amplifiers. A signal gain of 20 dB was obtained at a low bias current of 23.5 mA     

High-performance NMOS operational amplifier

A high performance operational amplifier 300 mil/SUP 2/ in area has been designed and fabricated in a standard n-channel silicon-gate enhancement/depletion MOS process. Specifications achieved include open-loop gain, 1000; power consumption, 10 mW; common-mode range within 1.5 V of either supply rail; unity-gain bandwidth, 3.0 MHz with 80/spl deg/ phase margin; RMS input noise (2.5 Hz-46 kHz), 25 /spl mu/V; C-message weighted noise -5 dBrnC; and 0.1-percent settling time, 2.5 /spl mu/s.     

High-speed GaAs operational amplifier

An operational amplifier has been designed and fabricated using GaAs MESFETs. This amplifier is a general-purpose monolithic GaAs op amp designed as as a stand-alone component. The amplifier has a differential input, an open-loop gain in excess of 60 dB, and is internally compensated. The high open-loop gain (60 dB at 100 kHz) was achieved by using gain stages with positive feedback. The op amp incorporates a current-mirror level-shifting stage which allows the op amp to operate over a wide power-supply range (/spl plusmn/5-9 V). Previous designs have diodes to achieve level shifting, a practice that precludes operation over a wide supply range. This op amp is a true analog to its silicon counterparts, but it has a higher gain-bandwidth product.     

Pseudo-class-AB telescopic-cascode operational amplifier

A novel class-AB architecture for single-stage operational amplifiers is presented. The structure employs a switched-capacitor level shifter to provide a signal-dependent current in the current source of the common-source amplifier. Applying this pseudo-class-AB approach to a telescopic-cascode opamp enhances the effective values of the slew rate and the transconductance and thus the opamp speed.     

Computer simulation of operational amplifier

A technique for the computer simulation of an op-amp is described. Results of the simulation of an inverting integrator configuration using this technique is also presented.     

A compact low noise operational amplifier for a 1.2 μm digitalCMOS technology

A compact low noise operational amplifier using lateral p-n-p bipolar transistors in the input stage has been fabricated in a standard 1.2 μm digital n-well CMOS process. Like their n-p-n counterparts in p-well processes, these lateral p-n-p transistors exhibit low 1/f noise and good lateral β. The fabricated op amp has an area of only 0.211 mm² with E_n=3.2 nV/√(Hz), I_n=0.73 pA/√(Hz), E_n and I_n 1/f noise corner frequencies less than 100 Hz, a -3 dB bandwidth greater than 10 MHz with a closed loop gain of 20.8 dB, a minimum PSRR (DC) of 68 dB, a CMRR (DC) of 100 dB, a minimum output slew rate of 39 V/μs, and a quiescent current of 2.1 mA at supply voltages of ±2.5 V. The operational amplifier drives a 1 kΩ resistive load to 1 V peak-to-peak at 10 MHz and has been used as a versatile building block for mixed-signal IC designs     

Design and applications of the operational floating amplifier (OFA): The most universal operational amplifier

The operational floating amplifier (OFA) is the most universal type of operational amplifier. Both input and output ports are floating ports, i.e., free from restrictive ground connections. The floating input port enables the OFA to accurately equate two voltages between the two input terminals, like a standard operational amplifier, but in addition to that the OFA is able to accurately equate two currents through the two terminals of the floating output port. Specific applications are given, such as current amplifiers, voltage-to-current converters, gyrators, hybrids, and filters. The concept of the OFA allows these analog transfer functions to be realized with the absolute minimum number of accurate internal and external elements necessary to accurately determine the transfer. The OFA does not need accurate internal matched elements, except for offset, to obtain accurate overall transfer functions. This is in contrast to other current-output devices, such as the current conveyer, which transfer depends on the accuracy of internal current mirrors. Several designs of class A and class AB OFAs based on different topologies are presented and compared. This paper gives an overview of the application, the specification, and the design.     

Wideband discriminator with operational amplifier

High-performance wideband low-frequency discriminators can be realised by the use of feedback. The principle of a discriminator with voltage negative feedback is presented.     

高速高增益运算放大器的设计及应用

本文设计了一种高速高增益放大器,该放大器通过增加全差分的共源共栅电路作为辅助放大器来提高运放增益,并采用频率补偿和钳位管相结合的技术改善运放的频响特性,使得运放在通频带范围内类似于单极点运放,大大减少了运放的转换时间.采用SMIC的0.35μm工艺模型进行仿真,结果表明,运放的直流增益达到110dB,带宽266MHz(负载电容 Cload=1pF),相位裕度55°,只需10ns即可达到0.1%的稳定精度,因而是一种有效的高速高精度运放的实现途径.     

DESIGN AND ANALYSIS OF INTEGRATED OPERATIONAL AMPLIFIER XD1531 WITH LOW NOISE AT LOW FREQUENCIES

Principles of design are described for the low frequency integrated operationalamplifler XD1531 with low noise. The procedures of design of both the circuit structure and the tran-sistor shape are considered. The first stage of the circuit is designed with the methods of low noise atlow frequencies. The measures which decrease noises, especially, the 1/f noise originating .from thesemiconductor surface state and defects, are used for the transistor structure design. With analysisand comparison to products here and abroad in characteristics, it is shown that XD1531 has a lowernoise index at low frequencies than others, and the effectiveness of design methods for bringing lownoises have been demonstrated.