负反馈放大器的自激振荡产生原因及消除

１自激振荡产生的原因及危害根据参考资料的讨论可知单级阻容耦合共发射极放大电路在中频区输出与输入的电压相位差是１８０°。负反馈引入后可以改善放大器的一些性能：如降低放大倍数，提高放大倍数的稳定性，改变输入输出电阻等。但不管情况如何负反馈的反馈信号总是削弱放大器的净输入信号。但是当负反馈的反馈深度D＝０时，将会出现反馈放大电路在没有信号输入的情况下会有信号输出，这种现象违背了放大器的输入输出关系，使放大器变为自激振荡。那么负反馈是D＞１的，为什么会出现D＝０的呢？这是因为单级共射放大器在中频段满足输…     

如何准确判定反馈电路的反馈形式

在电子电路的教学中,学生对反馈电路的学习比较困难,特别是判定反馈电路的反馈形式,是一个十分突出的难点。本文结合教学实际,提出了如何准确判定反馈电路反馈形式的方法,该方法使用方便,简单而准确。一、什么是反馈电路的反馈形式本文所说的反馈电路的反馈形式,是指反馈电路中反馈信号的输入方式与反馈信号的取样方式之组合形式。反馈信号与输入信号的联接关系有串联与并联之分,反馈信号从负载上的取样方式有电压与电流之分,组合起来有四种反馈形式,即:串联电流反馈,串联电压反馈,并联电流反馈,并联电压反馈。反馈电路反馈形式的判定,就是…     

负反馈效果与信号源内阻R_s关系的分析

<正> 不管什么形式的负反馈电路,反馈效果都与放大电路输入端信号源内阻R_a有着密切的关系,然而学生在学习这一问题时,其物理概念不清楚、理解模糊。为了帮助学生从物理概念上易于掌握反馈效果与信号源内阻R_a的密切关系,本文将从放大电路引入负反馈后,信号源内阻R_a对有效输入信号电压V_(bc)的影响程度进行定性和定量分析。     

反馈环的基本状况--写存器新析之一

将两个受外来信号控制的、串联成封闭回路的非门定义为反馈环将内、外输入信号以与(或)非门形式输入的反馈环定义为与(或)非环以与非环为例，从理论上阐明了反馈环的稳态、变态(非稳态)及其条件和判别方法。     

生命机体中的反馈调节

生物系统一律具有精巧的反馈机制,其精确度和复杂性是在任何非生物系统中都未见到的。这些反馈机制对外界刺激有反应能力,能调节代谢作用（能量的聚集与释放）并有控制生长、分化的能力。1．1反馈的概念所谓反馈,就是把系统输入的信息,作用于控制对象后,产｝的结果输送出来,并对信息的再输出发生影响的过程,从哲学高度讲,反馈就是结果对原因的反作田,如下图所示：正反馈：如果回送的信息与原输入的信息起的作用则问,使原输入信号增大,反馈的信号也增大,起到增强输入的作用,这就是正反馈。负反培：如果回送的信息与原输入的信息…     

反馈极性的基础理论研究

文章用方框图明确了输入信号、反馈信号等概念 ,分析了反馈极性的决定因素和直接效果 ,改进了传统的“瞬时极性法”。     

谈反馈与生物反馈

反馈是系统输出信息返回输入端，经处理，再对输出施加影响的过程：分为正反馈和负反馈，正反馈是使反馈信息与原信息起相同的作用，使总输入增大，信号加强，系统目标偏离，使偏差愈益加大，加剧了系统不稳定，导致振荡，它能放大控制作用。而负反馈是使反馈信息与原信息起相反的作用，使总输入减少，信号减弱，减弱控制作用，使系统目标偏离减小，使偏差缩小，纠正了偏差，使系统更加稳定。     

反馈极性的基础理论研究

文章用方框图明确了输入信号、反馈信号等概念，分析了反馈极性的决定因素和直接效果，改进了传统的“瞬时极性法”。     

基于状态观测器的非一致采样系统状态反馈预测控制

针对输入更新不等间隔的非一致采样系统,提出一种基于状态观测器的状态反馈预测控制算法．通过提升控制信号,设计了输入输出同周期的非一致采样系统的状态观测器,并且给出了提升控制信号前后观测器系数矩阵的关系．运用线性矩阵不等式方法,解决无穷时域二次型性能指标下的优化问题,给出了状态反馈预测控制器存在的充分条件．仿真结果证明了控制算法的有效性．     

关于负反馈放大器单向模型的第三个条件

在分析负反馈放大器时,往往要引进一个物理意义非常清楚的具有单方向性的框图模型(以下称其为单向性模型)如图1所示。 但是,上面的单向性模型的画出及由此得出的重要公式(1—1)是有条件的,正如几本有影响的教科书中指出的: 1、输入信号只能单方向通过基本放大器而不能通过反馈网络传至输出端。 2、输出信号只能单方向通过反馈网络而不能通过基本放大器传至输入端。 3、反馈系数F与信号源内阻R_s,和负载的R′无关。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.