一种基于外部特性的晶体管电路模型的构建方法

晶体管外部特性是指输入侧电压与电流间的关系和输出侧电压与电流间的关系.对晶体管放大电路中的晶体管输入/输出端口及其外部电路的电压-电流间关系进行图解分析,得到解的数学描述,再对微变增量用微分量代替,从而获得晶体管端口电压电流间的线性描述.使用基尔霍夫电压定律及电流定律对该线性描述进行解读之后,选用线性电阻、恒压源和受控电流源作适当连接,形成与解读结果相一致的反映放大电路中晶体管端口实际变量关系的电路模型.用于晶体管放大电路静态分析和动态分析的晶体管电路模型是这一模型的特殊情况.     

高频小信号谐振放大电路时域与频域对比分析

高频小信号谐振放大电路,主要是用来放大采集的微小的高频电压信号,但是放大器的负载不是线性电阻而是具有选频功能的谐振网络。所以谐振放大电路能够对不同频率的信号进行不同增益的放大,在信号的选择等方面具有重要的作用。文章从时域以及频域两个方面对谐振放大电路进行对比分析。     

E类放大电路中晶体管的功率损耗

在理想情况下,E类放大电路的效率可以达到100%,因此E类放大电路适用于高功率,高频率电路的设计,但在实际情况下,由于所有的器件都不是理想的。例如,电感、电容中会有寄生电阻的存在,晶体管的饱和电压,饱和电阻以及集电极电流的下降时间不为零,这些因素的存在都会导致E类放大电路的效率降低,但当电路的负载匹配且处于谐振状态,则引起电路功率损耗的主要因素也就是晶体管中的功率损耗。对E类放大电路中由晶体管引起的损耗进行分析,并得出简单的估算方法,并用实验的方法验证。     

中周模型在Multisim中的实现

为了解决用Multisim仿真高频单谐调谐振放大模块无中周模型的问题,通过对高频小信号放大模块的理论分析,总结出用LC电路模型替代中周电路模型的方法,做了高频单谐调谐振放大模块的仿真实验,获得了正确的仿真实验结果,该方法对用Multisim仿真高频谐调谐振放大模块具有借鉴意义。     

晶体管放大电路入门：单管放大器

怎样把晶体管的电流放大作用转换成电压放大作用?这就必需外接元件构成放大电路,其中最简单的就是单管放大器。基本单管放大器的电路如图1所示.其中晶体管T作电流放大,将输入基极电流放大p倍产生输出集电极电流。R_B叫基极偏置电阻,由电源Ec通过R_B产生直流基极电流I_(BQ)     

晶体管收音机变频级故障分析与检修

<正> 变频级是超外差式收音机的关键电路,其主要任务是把调谐回路选出来的某一频率的高频信号,转变为固定频率(465kHz)的中频信号,送到中频放大级进行放大。 变频级电路结构与原理 为了将高频信号转变成固定中频信号,就要在变频级电路中设置本机振荡器和混频器,并且要把由天线接收的输入信号和本机振荡器产生的本振信号同时加至混频器进行混频,然后通过调谐回路选择出所需要的固定中频信号,其电     

UWB LNA的增益平坦化及稳定性的反馈技术

从异质结晶体管(HBT)的小信号模型着手,得到了几种不同反馈形式下HBT的S参数解析表达式。通过对比不同反馈形式的仿真结果,分析了各种反馈形式对S参数的影响,并着重研究了反馈技术对电路稳定性以及对超宽带低噪声放大器(UWB LNA)增益平坦度的影响。结果表明,采用串联电阻和电感或并联电阻和电容的电抗性负反馈,可以使S21的幅度随着频率的增大而逐渐上升,从而补偿了晶体管本身高频增益的下降,同时,也提高了整个电路的稳定性。采用这种反馈结构,设计了一款3～10 GHz超宽带低噪声放大器。仿真结果表明,该放大器在整个频带范围内无条件稳定,传输增益较高,增益平坦度较好,噪声系数较低,是一款无条件稳定并有着较好增益平坦度的超宽带低噪声放大器。     

晶体管放大器静态工作点稳定性的判定方法

面对在几个稳定静态工作点的电路中选择时,如何迅速判定各电路静态工作点稳定性能的优劣,是一个值得弄清的重要问题。本文给出了求出典型放大器偏置电路的戴维南等效电路,依此等效电路可直接看清电路工作时的物理意义,进一步判定各个放大电路静态工作点稳定性能的优劣。     

数字功放原理

<正> 数字功放也称D类功放,与模拟功放的主要差别在于功放管的工作状态。传统模拟放大器有甲类、乙类和甲乙类、丙类等。一般的小信号放大都是甲类功放,即A类,放大器件需要偏置,放大输出的幅度不能超出偏置范围,所以,能量转换效率很低,理论效率最高才25％。乙类放大,也称B类放大不需要偏置,靠信号本身来导通放大管;理想效率高达78.5％。但因为这样的放大,小信号时失真严重,实际电路都要略加一点偏置,形成甲乙类功放,这么一来效率也就随之下降。虽然高频发射电路中还有一种丙类,即C类放大,效率可以更高,但电路复杂、音质更差,音频放大中一般都不采用。这几种模拟放大电路的共同特点是晶体管都工作在线性放大区域中,它按照输入音频信号的大小控制输出的大小,就像串在电源与输出间的一只可变电阻,控制输出,但同时自身也在消耗电能。     

基于电压阀和电流阀模型的晶体管放大电路分析

依据已经提出的电压阀和电流阀两种非线性电路模型以及由电压阀和电流阀构造出的晶体管模型,进一步对各种晶体管放大电路进行了非线性模型等效,并在等效的模型电路基础上,研究晶体管放大电路的静态工作点计算方法、动态参数计算方法.该方法具有电路直观、概念清晰、分析计算准确等特点,而且能够判断出晶体管是否截止或饱和、动态工作范围大小等.     

Computer-aided design and optimization of a broad-band high-frequency monolithic amplifier

A monolithic wide-band amplifier for applications in counters from dc to UHF frequencies has been realized. The use of computer-aided design techniques, using a transistor model, and a broad-band feedback configuration has resulted in a monolithic amplifier that previously could only be constructed in hybrid form. This paper describes the development of a new high-frequency transistor model and a dc-coupled monolithic high-frequency amplifier that incorporates a final masking step option to obtain a maximally flat response over a 700-MHz bandwidth.     

The Logarithmic Tunnel Diode Amplifier

This paper describes design techniques and performance characteristics of a high-frequency logarithmic amplifier. The technique used is to sum the detected outputs of each amplifier in a cascade in order to generate a straight line segment approximation to the desired logarithmic responses. It is shown that the normal RF characteristics of tunnel diode amplifiers approximate this performance when operated at minimum negative resistance. A 3.05 GHz tunnel diode amplifier is designed using these principles, and its performance is described in this paper. It is shown that the amplifier has an experimental error of /spl plsmn/0.625 dB over a compression range of 60 dB input signal power.     

On a surface wave amplifier for negative resistance devices

A traveling-wave negative resistance amplifier is proposed using a corrugated surface wave structure. A simple gain equation is derived based on a two-dimensional model. The proposed amplifier is simple to construct and is capable of high-power operation.     

A High-Frequency MOS Transistor Model and its Effects on Radio-Frequency Circuits

Accurate modeling and efficient parameter extraction of a small signal equivalent circuit of MOS transistors for high-frequency operation are presented. The small-signal equivalent circuit is based on the quasi-static approximation which was found to be adequate up to 10 GHz for MOS transistors fabricated by a 20 GHz cutoff frequency technology. The extrinsic components and substrate coupling effects are properly included. Direct extraction is performed by Y-parameter analysis on the equivalent circuit in the linear and saturation regions of operation. A low-noise amplifier is used to illustrate the effects on circuit performance due to accurate inclusion of extrinsic components in the model. Good agreement between simulated results and measured data on high-frequency transistor characteristics has been achieved.     

一种S波段宽带GaN放大器的设计

氮化镓功率管的宽带隙、高击穿电场等特点,使其具有带宽宽,高效特性等优点。为了研究GaN功率放大器的特点,使用了AgilentADS等仿真软件,进行电路仿真设计,设计制作了一种s波段宽带GaN功率放大器。详述了电路仿真过程,并对设计的宽带GaN功率放大器进行测试,通过测试的实验数据表明,设计的宽带放大器在s波段宽带内可实现功率超过44dBm的功率输出,验证了GaN功率放大器具有宽带的特点。     

Linear operation of a p-n-p-n tetrode

At the present time all p-n-p-n devices are used exclusively as switches. The p-n-p-n tetrode however, is also capable of operating as a linear amplifier. A model describing the operation of such a device as a semiconductor tetrode amplifier is presented. The equations characterizing this model are based on the physical structure of a commercially available silicon planar p-n-p-n tetrode; they are used 1) to derive the device terminal characteristics, 2) to synthesize small-signal equivalent circuits suitable for low-frequency operation (h-parameter circuit) and for high-frequency operation (bridged hybrid-π circuit), 3) to study the dependence of short-circuit gains of the tetrode on the dc biasing currents and frequency, and 4) to obtain a stability condition which must be satisfied to insure that the operation of the device is restricted in its OFF state where it can function as a small-signal linear amplifier. The theoretical results are in close agreement with experimental values.     

High-frequency CMOS amplifier with improved bandwidth performance

A high-frequency CMOS amplifier is proposed which can be used as a gain stage in RF front-ends. The circuit is based on a traditional transconductance amplifier unconventionally arranged to achieve both accurate input biasing and single-to-differential conversion. It takes advantage of an innovative approach to greatly improve frequency performance. Owing to this technique, the operating frequency of a basic amplifier in a 0.8 μm CMOS process could be extended from 290 to 650 MHz without affecting the gain     

4～8GHz宽带单片集成低噪声放大器设计

基于0.15μm GaAs PHEMT工艺设计了一款C波段宽带单片集成低噪声放大器。电路由三级放大器级联而成,三级电路结构均使用电阻自偏压技术来实现单电源供电,它既可保证PHEMT管处于低噪声高增益的工作点,又可将所有元器件集成在单片GaAs衬底上,解决了供电复杂的问题。第三级电路采用了并联负反馈结构,降低了带内低频端...