Externally linear current amplifiers

This paper describes a method to implement externally linear internally non-linear (ELIN) current amplifiers. Two novel schemes of ELIN current amplifier circuits are proposed, including hyperbolic sine (SINH) and hyperbolic tangent (TANH) circuits. The obtained linear input-current ranges of SINH and TANH circuits are 400?µA_p-p with total harmonic distortion (THD) less than 2% and 140?µA_p–p with THD less than 0.2%, respectively, both at the input frequency 1?kHz. Also, the current gains of the proposed circuits can be varied either in positive or negative region by adjusting the dc bias currents. Their current gains are tunable in the range of ?10?A/A to 10?A/A and insensitive to temperature. Simulation results show that the performance of the circuits are as good as expected.     

集成电流反馈运算放大器的应用与实践特性及应用设计

介绍电流反馈运算放大器包括电路组成，工作原理及有关的应用设计。     

Applications of the current feedback operational amplifiers

The current feedback operational amplifiers (CFOAs) are receiving increasing attention as basic building blocks in analog circuit design. This paper gives an overview of the applications of the CFOAs, in particular several new circuits employing the CFOA as the active element are given. These circuits include differential voltage amplifiers, differential integrators, nonideal and ideal inductors, frequency dependent negative resistors and filters. The advantages of using the CFOAs in realizing low sensitivity universal filters with grounded elements will be demonstrated by several new circuits suitable for VLSI implementation. PSPICE simulations using the AD844-CFOA which indicate the frequency limitations of some of the proposed circuits are included.     

A floating generalized impedance converter with current feedback operational amplifiers

A novel generalized impedance converter topology realized using current feedback operational amplifiers is introduced in this paper. The main offered benefit, in comparison to the corresponding already published structure, is that frequency dependent negative resistors can now be also realized. Other benefits are the requirement for only grounded capacitors, the lower component count, and the capability of tuning through a grounded resistor. The correct operation of the proposed GIC has been verified through a design example, where a 3rd-order lowpass filter has been topologically simulated.     

New precision rectifier circuits with high accuracy and wide bandwidth

Two new circuits for precise full-wave rectification are presented. The first is based on a current feedback amplifier with a new current-mode absolute-value circuit in its feedback loop. The second utilizes an operational conveyor working in conjunction with a current-mode absolute-value circuit in a new configuration. Both circuits have high accuracy and wide bandwidth, giving undistorted rectified waveforms up to 500?kHz in the first case and 1?MHz in the other. Additionally, both systems have high sensitivity, being able to full-wave rectify signals with amplitudes as small as 5?mV peak at 100?kHz. Finally, the new systems have excellent temperature stability, low offset output voltage and are suitable for IC fabrication.     

电流型运算放大器在应用电路中的特性研究

文中简要介绍了电流型运放的特性,着重对电流型运放的应用电路进行测试,研究电流型运放的应用特性。实验中,选择典型电流型运放及电压型运放构建负阻变换器、电压跟随器和同相比例放大器,通过对此3类应用电路的测试,分析、总结运放参数对特殊应用电路的影响,为电路设计者在具体电路的设计中恰当选择适合的放大器提供参考。     

New topology for implementing bandpass,bandstop and allpass filters with CFAs

In this brief, a new filter topology based on current feedback amplifiers is presented and compared with its operational amplifier counterpart. The circuits arising from the new topology have the important advantage that access to the Z node of the current feedback amplifier is not required, as is the case with many existing current feedback amplifier filter circuits. The operation and requirements for each of the filters are described. Theoretical results and circuit limitations are discussed and verified with experimental results. In one experiment a bandpass filter with a calculated Q and centre frequency of 20 and 158.53 kHz, respectively was built using the OPA2607 dual CFAs IC. Measured results yielded a Q of 20.153 at a centre frequency of 148.62 kHz showing close agreement with theory.     

Cascadable current mode instrumentation amplifier

In this paper, a Current Mode Instrumentation Amplifier (CMIA) is presented. The proposed circuit employs two Extra X Current Controlled Current Conveyors (EX-CCCII) and a single grounded resistor. The circuit offers a wide differential-gain bandwidth, wide CMRR bandwidth, and electronically tunable differential gain. The circuit offers cascadibility feature with input impedance of 2.167 kΩ which is very small in comparison to the output impedance of 2.17 MΩ. Simultaneously, a Transresistance (TR) instrumentation amplifier is also obtained with the features of electronically tunable high differential gain and wide bandwidth. The effect of non-idealities of EX-CCCII on the circuit performance is also analysed. The validity of the proposed circuit is verified through PSPICE simulations using 0.25 µm parameters with a supply voltage of ±1.25 V. Also, the circuit is verified by experimental results.     

增益带宽可调放大器

本论文介绍一款高指标的增益带宽可调放大器的设计与制作。设计采用多重措施来降低噪声,提高效率,并且采用负反馈思想抑制零点漂移。实测表明,设计出的增益带宽可调放大器各项指标能很好地达到设计要求,具有一定的实用性,为工业生产和电子竞赛提供可靠参考。     

用线性变换运算电流放大器(TOCA)的电流处理电路

本文描述最近引入的新的多功能有源器件—线性变换运算电流放大器的基本性质以及它在电流处理电路中的应用.     

Band-pass filter with high quality factor based on current differencing transconductance amplifier and current amplifier

This paper presents second order band-pass filter with high quality factor. Its high quality factor is provided by feedback circuit. The used second order filter is modified so that filters outputs through capacitor can be obtained to high impedance output. Thereby, there is no need the extra active element to obtain filter outputs. Also, the output stage of current differencing transconductance amplifier have only X− terminals instead of X+ and X− terminals. Furthermore, the quality factor of the band-pass filter with feedback circuit is increased by feedback gain consisting of only four transistors. Besides, to examine effects of parasitic elements, non-ideal and sensitivity, the overall structure is investigated deeply. Working conditions and boundaries of the overall structure is also defined. The simulation demonstrates good agreement between the theoretical expectations and simulation results.     

A high-speed current conveyor based current comparator

In this paper, a new high-speed current mode comparator based on inherent current conveyor and positive feedback properties is presented. This novel approach has resulted in major reduction of the response time and hence a wide band application of the circuit. Simulation results using HSPICE and 0.18 μm CMOS technology with 1.8 V supply confirms a propagation delay of less than 0.4 ns in the high frequency range of 700 MHz with 158 μw power dissipation. Under the above conditions, the accuracy of the input current is as low as 50 nA.     

Multiple-loop feedback filters using current feedback amplifiers

Novel high-order filter topologies realised by employing current feedback operational amplifiers as active elements are introduced in this article. These are constructed from multiple-loop feedback paths and could be utilised for the realisation of filters of arbitrary order and type. An offered benefit is the requirement for employing only grounded capacitors and resistors. Two design examples are provided and the correct operation of the corresponding topologies has been evaluated through experimental results.     

High-speed CMOS unity-gain current amplifier

A high-performance CMOS unity-gain current amplifier is proposed. The solution adopts two feedback loops to reduce the input resistance and a nested-Miller technique to provide frequency compensation. A design example using a 0.8 μm process and a 2 V supply is given and SPICE simulations show a bandwidth of 75 MHz, no slew-rate limitations and a settling time better than 50 ns, irrespective of the current amplitude. Input and output resistances are better than 0.1 Ω and 15 MΩ, respectively. The input-referred white noise spectral density is .     

Novel input stages for current feedback operational amplifiers

This paper considers the trade-offs involved in the design of six new input stages intended to improve the performance of a current feedback operational amplifier (CFOA), over that possible using an established input circuit configuration, with respect to three major characteristics, viz, common mode rejection ratio (CMRR), offset voltage and slew-rate.     

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.     

THE DESIGN OF BALANCED AMPLIFIER BASED ON COMMON-MODE FEEDBACK

The balanced operational amplifier including its merits and designing methods is discussed by comparing its performance to a conventional differential output amplifier when used in a single balanced stage. A balanced OTA circuit design is also presented.     

Design and analysis of a flat gain and linear low noise amplifier using modified current reused structure with feedforward structure

In this paper, a Low Noise Amplifier (LNA) with the current reused topology is proposed for wideband applications. To increase input impedance matching common source with inductive degeneration and RC shunt feedback structure is used. To extend the bandwidth, inductive series peaking technique is utilized. In the next stage, two parallel structure is hired to have a high voltage gain with low power consumption in addition to improve linearity. Also, by using the self-forward-body-bias (SFBB) technique, supply voltage is reduced and as a result power consumption is decreased further. The proposed LNA exhibits the high and flat gain of 14.7–15.4 ​dB, input return loss of less than −11 ​dB and noise figure range of 2.3–4.4 ​dB from 1 ​GHz up to 8 ​GHz. It consumes 5.4 ​mW from a 1.2 ​V power supply. The achieved IIP3 range for the proposed LNA is 0 ​dBm up to +2.7 ​dBm. The proposed LNA occupies 0.45 ​mm² in 0.18-μm CMOS technology.     

Gain improvement in operational transconductance amplifiers using Graded-Channel SOI nMOSFETS

This paper studies the performance of operational transconductance amplifiers (OTAs) fabricated with Graded-Channel (GC) SOI nMOSFETs and designed to provide high open-loop voltage gain or high gain-bandwidth characteristics. Different design targets were taken in account such as similar power dissipation, transconductance over drain current ratio and die area. Comparisons with OTAs made with conventional SOI nMOSFETs, are performed showing that the GC OTAs presents larger open-loop voltage gain without degrading the phase margin, unit gain frequency and slew rate simultaneously with a significant required die area reduction depending on L_LD/L ratio used. Circuit simulations and experimental results are used to qualify the analysis.     

High slew rate current mode transconductance error amplifier for low quiescent current output-capacitorless CMOS LDO regulator

This paper presents a CMOS low quiescent current output-capacitorless low-dropout regulator (LDO) based on a high slew rate current mode transconductance amplifier (CTA) as error amplifier. Using local common-mode feedback (LCMFB) in the proposed CTA, the order of transfer characteristic of the circuit is increased. Therefore, the slew rate at the gate of pass transistor is enhanced. This improves the LDO load transient characteristic even at low quiescent current. The proposed LDO topology has been designed and post simulated in HSPICE in a 0.18 µm CMOS process to supply the load current between 0 and 100 mA. The dropout voltage of the LDO is set to 200 mV for 1.2–2 V input voltage. Post-layout simulation results reveal that the proposed LDO is stable without any internal compensation strategy and with on-chip output capacitor or lumped parasitic capacitances at the output node between 10 and 100 pF. The total quiescent current of the LDO including the current consumed by the reference buffer circuit is only 3.7 µA. A final benchmark comparison considering all relevant performance metrics is presented.