Multisim在静态工作点稳定电路分析中的应用

本文从固定偏置电路出发,首先通过Multisim温度扫描分析其温度稳定性较差的原因,然后通过引入电流串联负反馈,分析射极偏置电路工作点的稳定性及动态性能的变化。为了在稳定静态工作点的同时兼顾动态性能,基于Multisim,对完全旁路电路和部分旁路电路进行比较分析。同时,利用交流分析功能,对引入反馈前后的通频带变化进行比较,最终使学生对静态工作点稳定的过程有了深入的理解。     

工作点稳定的偏置电路

前面叙述单管放大器的原理时已经指出:晶体管在静态时必须建立位于放大区中部的静态工作点Q,以使晶体管具有电流放大作用,并使交流信号输入时不会产生输出信号的失真,在放大电路中建立静态工作点,即产生直流偏置电流I_(BQ)与H_(CQ)的电路叫偏置电路。一、静态工作点不稳定的原因及对放大性能的影响:上面讲的单管放大器电路工作点是不稳定的,当环境温度上升,     

静态工作点稳定性对射极输出器动态性能的影响

鉴于电子技术教材的阻容耦合射极输出器都是静态工作点不稳定的电路形式,都没有分析静态工作点的稳定性对电路动态性能影响的问题,因而有射极输出器是否需要稳定的静态工作点的疑点问题.针对疑点问题,研究了射极输出器的电压放大倍数、输入电阻、输出电阻等三大动态性能指标的数值范围及与静态工作点的关系,得出射极输出器静态工作点的稳定性对电路动态性能影响很小、射极输出器的偏置电路可采用简单构成形式的结论.     

用单环反馈模型进行工作点稳定性的定量分析

利用负反馈稳定电路的工作点,是常见的一种重要方法。既然如此,对于具有直流反馈的电路,就可用单环反馈模型进行工作点稳定度的定量分析,(即计算不稳定系数S≈(△I_C/△I_(CBO))、S′≈(△I_C/△V_(BE))和 S″≈(△I_C/△β),见参考文献),现举两例分析如下:一、射极偏置电路图1(a)为射偏置电路,(b)为分析工作点稳定性的等效电路。     

静态工作点与放大电路性能的关系

以单管共射放大电路为例,讨论放大电路中静态工作点与动态参数、输出波形的关系,得出调整静态工作点和动态参数的可行办法,有利于理解和掌握模拟放大电路的原理与实质。     

基于Multisim 10的单管共射放大电路静态分析

静态工作点是"模拟电子技术"课程中的教学重点,也是教学难点。利用仿真Multisim 10软件,对共发射极基本放大电路进行静态仿真测试分析,使学生在基本放大电路的学习中对静态工作点的概念、静态工作点对放大电路的重要性和必要性有比较清晰正确的理解,对共发射极放大电路在不同工作情况下的特点有一个比较全面的认识。研究表明,利用Multisim 10强大的分析功能对电子电路进行计算机仿真,可以提高教学质量和教学效果。     

基于Multisim 10仿真的负反馈放大电路

Multisim 10是美国国家仪器有限公司最新推出的EDA软件,它具有更加形象直观的人机交互界面,几乎能够100%地仿真出真实电路的结果。负反馈的多级放大电路是模拟电路中比较经典的电路,在此采用实验法,借助Multisim 10仿真平台,将具有负反馈的两级放大电路进行仿真,探索加入负反馈的电路特点。分析电路静态工作点和动态参数的变化以及加入负反馈后对电路放大倍数的影响,说明负反馈电路能稳定电路的静态工作点,放大倍数降低了,但频带得到了扩展,在实际设计电路时具有深远的现实意义。     

阻容耦合放大电路里耦合电容及旁路电容的深度分析

具有稳定静态工作点的单管共射放大电路是模拟电路里的一款经典电路,包含很多的模拟电路知识,其中耦合电容和旁路电容是该电路的重要组成部分。通过电容的特性使电路的交直流通路进行分离,使得该电路的动态性能得到很好的改善。文章将对该电路中耦合电容及旁路电容的工作原理及对频率特性的影响进行深入讨论,并结合仿真软件multisim12进行仿真分析。     

晶体三极管电路设计与探讨

阐述了三极管放大电路重理论分析,轻参数调整和参数设计,本文以共发射极分压式静态工作点稳定电路为例介绍一种三极管电路快速设计的原理、方法和步骤,利用软件仿真进行参数调整,经测试放大电路参数优良、工作稳定、方法简单方便、可操作性强,得到广泛应用。     

基于性能退化的功能电路软故障可靠性分析

通过对电子功能电路退化量分布的分析,提出了一种基于性能退化的功能电路软故障可靠性分析方法,并以某型雷达放大电路功能电路为例进行了试验,根据静态工作点的变化所引发的软故障,进行了电路的软故障可靠性分析.     

DC boosting effect of active bias circuits and its optimization for class-AB InGaP-GaAs HBT power amplifiers

In this paper, dc sourcing capability (DSC), which is a very important consideration in design of active bias circuits for power amplifiers based on bipolar technologies, will be explained. The nonlinear effect of bias circuits on the dc sourcing characteristics has been analyzed with simplified circuits for power amplifiers using the Volterra series. The analysis shows that the second-order distortion generated by a bias buffer transistor can boost bias level of the RF transistor to compensate finite DSC available in the absence of this effect. The bias-level boosting due to RF injection can be optimized by tuning the value of a series resistor between the emitter of the buffer transistor and the base of the RF transistor. Amplifiers with different series resistors have been implemented and tested with an IS95-B code-division multiple-access signal at the cellular band (824-849 MHz). The experimental results verify that a circuit-level optimization for the second-order distortion of the bias circuits is very important for optimizing the linearity and efficiency of the HBT amplifiers.     

Comparison of hot electron and related amplifiers

It is proposed that novel amplifiers be compared with each other and with existing amplifiers on the basis of as many figures of merit as are calculable. The bipolar transistor; field-effect transistor; Schottky-emitter, space-charge-limited-emitter, and tunnel-emitter, metal-base, hot-electron amplifiers are compared with respect to frequency cutoff and maximum frequency of oscillation. Using reasonable ground rules for the comparison, the amplifiers rank (with respect to frequency cutoff) in the order: Schottky emitter, bipolar transistor, space-charge-limited emitter, and tunnel emitter. With respect to maximum frequency, the amplifiers rank in the order: Schottky emitter; space-charge-limited emitter; tunnel emitter and bipolar transistor equivalent; and field-effect transistor.     

Comprehensive study of multiband unconditional stabilization of common-source and common-gate MESFET transistors using feedback

The use of a new feedback scheme to achieve unconditionally stable MESFET transistors from 0 GHz until cutoff is presented. The methodology is applied for both common-source and common-gate MESFET transistor configurations. Analytical formulation of the stabilization methodology is presented. In addition, two coplanar-waveguide-based amplifiers were designed to operate at Ka-band, monolithically fabricated, and tested, thus, verifying the methodology. The study includes the effects of the bias change on the feedback amplifier stability performance.     

Gain-Bandwidth Limitations of Microwave Transistor Amplifiers

Gain-bandwidth limitations of broad-band single-stage microwave transistor amplifiers are related to a simple transistor circuit model, to constraints on characteristic impedance in a distributed-element equalizer, and to the line lengths of this equalizer. The gain-bandwidth performance of commensurate distributed-element equalizers is compared with the performance of a lumped-element equalizer, and four distributed-element design examples are presented, including two commensurate equalizers and two computer-optimized networks.     

Synthesis of broadband microwave transistor amplifiers

The design of broadband microwave transistor amplifiers is discussed in terms of direct synthesis of distributed commensurate matching networks. Examples are given for both single-stage and 2-stage amplifiers, using ladder networks realisable in stripline form.     

射频宽带低噪声放大器的设计与仿真

介绍了一种射频宽带低噪声放大器的设计过程,包括稳定性分析、偏置电路设计和匹配电路设计等内容.设计采用E-PHEMT晶体管(ATF-55143)器件模型和其他元件模型.通过采用ADS技术进行电路和电磁仿真,结果表明设计的放大器完全满足性能指标要求.     

Lumped Elements in Microwave Integrated Circuits

The use of lumped rather than distributed elements affords a considerable size reduction (typically a factor of 10 in area) in L- and S-band microwave integrated circuits. The electrical performance of such lumped elements is shown to be good enough to warrant their use in many applications where the size advantage or the resultant cost advantage is important. Miniature elements have been constructed which behave as true lumped reactive components up to at least 2.5 GHz. These elements have been evaluated using an impedance measurement method. Both inductors and capacitors have exhibited Qs greater than 50 at lower S band. Single-stage transistor power amplifiers at 2 GHz have been breadboarded using a simple arrangement of the lumped elements to match the measured impedances of the transistor pellet. These amplifiers have had gains as high as 4.7 dB at 2 GHz. The transistor used typically exhibits about 5 dB of gain in conventional coaxial circuitry. The loss in the lumped element matching networks has been about 0.5 dB greater than the loss in the distributed matching networks used in a microstrip amplifier built with the same type transistor. It is expected that the lumped circuit loss can be reduced as improved components are developed.     

Harmonic and intermodulation performance of MoS2FET- and GFET-based amplifiers

This paper presents a simple mathematical model for the output–input voltage characteristic of the graphene field effect transistor (GFET)- and the molybdenum disulfide field effect transistor (MoS₂FET)-based inverting amplifiers. The model, basically a Fourier series, yields closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output voltage resulting from a multisinusoidal input voltage. The special case of a two-tone equal-amplitude input voltage is considered in detail. The results show that the harmonic and intermodulation performance of the complementary GFET- and the MoS₂FET-based inverting amplifiers is strongly dependent on the bias voltage and the amplitudes of the input tones with the third-order intermodulation component dominating over a wide range of the input voltage amplitudes.     

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

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.