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论文题目：Tutorial questions exercise.
论文语种：英文
您的研究方向：理工
是否有数据处理要求：否
您的国家：英国
您的学校背景：伯明翰城市大学 排名中等
要求字数：2000
论文用途：本科课程论文 BA Assignment
是否需要盲审（博士或硕士生有这个需要）：否
补充要求和说明：做CWK2 的部分，一共10个问题，时间有点紧


1. (a) Define a closed loop amplifier.
(b) A negative feedback amplifier is to have a voltage gain of 100. What feedback fraction is required if the open loop gain is 430?
Answer:
(a) To improve the basic amplifier’s energy, we can introduce a reverse signaling pathway from the input of the amplifier to the output. This pathway constitutes a network called the feedback network, and this reverse signal is called the feedback signal transmission. The amplifier that formed by the basic amplifier and feedback network is called the closed-loop amplifiers or feedback amplifier.
(b) The relation among open-loop gain AOL, closed-loop gain ACL and feedback factor βis:
ACL=AOL/（1+β*AOL）
So we can get the conclusion:
β= （AOL/ ACL—1）/ AOL
                  = （430/100—1）/430
                  = 0.00767

2. Describe, using circuit diagrams, how a feedback voltage may be derived from the output of an amplifier. Show how the way in which such feedback is derived affects the output resistance of the amplifier.

3. Using suitable diagrams show how negative feedback may be applied to the input terminals of an amplifier. Show the effect each of the methods you describe has on the input resistance of the amplifier.

4. A feedback amplifier is one in which the output signal is sampled and fed back to the input to form an error signal that drives the amplifier. The basic block diagrams of non-inverting and inverting feedback amplifiers are shown in Fig. 1.

(a) An amplifier has an open loop gain of 2 x 105 and an input resistance of 50 kΩ. When negative feedback is applied in series with the input, the gain is reduced to
5 x 102. Find (i) the feedback fraction β, (ii) input resistance with feedback.
(b) What effect does negative feedback have on the bandwidth of an amplifier?

                             Fig.1

Answer:
(a)  (i) The relation among open-loop gain AOL, closed-loop gain ACL and feedback factor βis:
ACL=AOL/（1+β*AOL）
    We can get: β= （AOL/ ACL—1）/ AOL
                  = （2*10¬¬¬¬¬5/（2*102）—1）/（2*10¬¬¬¬¬5）
                  = 0.005
(ii)    Rif = Ri *（1+β*AOL）
          = 50 *( 1+ 0.005*2*10¬¬¬¬¬5）
          =50  MΩ
(b) In essence, bandwidth limitation is due to different frequency amplifier signal showing a different magnification. Negative feedback can stabilize closed-loop gain, so it can also effect on the decrease magnification that caused by the frequency increases (or decreases). In other words, it can本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。