一种超低功耗电流反馈运算放大器

设计了一种新型的基于第二代电流传输器CCⅡ-的超低功耗电流反馈运算放大器,并采用TSMC0.6μmCMOS工艺,利用Hspice对整个电路进行了仿真。在±1.5V电源电压工作条件下,该放大器的转换速率达到28.57V/μs,并且在闭环工作状态下具有恒定的带宽。     

An active inductor employing a new four terminal floating nullor transconductance amplifier (FTFNTA)

ABSTRACT

In this scientific study, a new analog active building block named as four terminal floating nullor transconductance amplifier (FTFNTA) is implemented. The FTFNTA design offers a combined essence of both traditional four terminal floating nullor (FTFN) and an operational transconductance amplifier (OTA). The FTFNTA design is extended for the design of a lossless floating and grounded inductor simulator with few passive components. In addition, the performance and usefulness of the proposed inductor topology are also expanded for active filter applications: higher-order Butterworth high-pass filter and current mode multifunction filter. The functionality of the CMOS-based FTFNTA is integrated with a 0.18 µm Taiwan Semiconductor Manufacturing Company (TSMC) CMOS technology. Moreover, the FTFNTA is also realised using the current feedback operational amplifier (CFOA/AD844) and OTA (OTA/CA3080) of a commercially available IC to test the viability of the proposed inductor design. Finally, an application based on the inductor topology and its impedance characteristics are well analysed via PSPICE simulation.     

Theoretical study of the circuit architecture of the basic CFOA and testing techniques

This paper examines the closed-loop characteristics of the basic Current-Feedback Operational Amplifier (CFOA), and in particular, the dynamic response. Additionally, it also examines the design and advantages of the CFOA regarding its ability to provide a significantly constant closed-loop bandwidth for closed-loop voltage gain. Secondly, the almost limitless slew–rate provided by the class AB input stage that makes it superior to the voltage-mode operational amplifier (VOA) counterpart. Additionally, this paper also concerns the definitions and measurements of the terminal parameters of the CFOA, regarded as a ‘black box’. It does not deal with the way that these parameters are related to the properties of the active passive and active components of a particular circuit configuration. Simulation is used in terminal parameter determination: this brings with it the facility of using test conditions that would not normally prevail in a laboratory test on silicon implementations of the CFOAs. Thus, we can apply 1mA and 1mV test signals from, respectively, infinite and zero source impedances that range in frequency from d.c to some tens of GHz. Also, we assume the existence of resistors with identical Ohmic value and very high value ideal capacitors. Where appropriate, practical test methods are referred to physical laboratory prototypes.     

On the Realization of Simulated Inductors with Reduced Parasitic Impedance Effects

In this paper, a method for reducing the parasitic impedance effects of the current feedback operational amplifiers (CFOAs) in an inductor simulator at low frequencies is proposed. Also, two novel grounded inductors employing a current follower (CF) and a second generation current conveyor (CCII) are given to illustrate the parasitic reduction technique clearly. The low frequency restrictions of the proposed inductors due to terminal parasitic resistances can be improved by using the presented parasitic impedance reduction technique. SPICE simulations show that the presented inductor employing CFOAs in a voltage-mode (VM) band-pass and high-pass filter application has lower parasitic effects at low frequencies. In addition to simulation results, experimental test results are given to verify the theory.     

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.     

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.     

Micropower high current‐drive class AB CMOS current‐feedback operational amplifier

A novel CMOS current‐feedback operational amplifier (CFOA) aimed to low‐power applications is proposed. The use of a compact class AB implementation allows high current‐drive capability and simultaneously very low quiescent power consumption. Measurement results of a fabricated prototype show for an inverting configuration a closed‐loop bandwidth of 1 MHz independent of gain setting, and a slew rate of 2V/µs for a load capacitance of 30 pF and a quiescent power consumption of 264µW. Copyright © 2010 John Wiley & Sons, Ltd.     

Bipolar Current Feedback Amplifier: Compensation Guidelines

The aim of the paper is to discuss in detail the compensation of the current feedback amplifier (CFOA). The approach is suitable for a pencil-and-paper compensation and takes into account both resistive and capacitive feedback. The frequency limitation inside the CFOA and due to a load capacitor are also considered. The feature of the CFOA which can be simply compensated for when it is configured as a differentiator is also exploited. To validate the proposed strategies, Spice simulations were performed on the fundamental CFOA topologies, and some of them are included and discussed in the paper.     

Effect of thickness on fracture criterion in general yielding fracture mechanics

In this research work, the effect of thickness on fracture criterion is studied for extra deep drawn (EDD) steel sheets. Experimental results are generated on fracture toughness of EDD steel sheets using compact tension specimens and a ‘maximum load’ as a fracture criterion. Critical crack tip opening displacement (CTOD) is found with the help of three methods: plastic hinge model (PHM), crack flank opening angle (CFOA) and finite element model (FEM). The fracture toughness is found to increase with increase in thickness of specimens. The fracture behaviour exhibited characteristics of general yielding fracture mechanics.