NPTEL Videos and UNIT 1 Assignment

Watch these NPTEL (IIT Madras) videos from You Tube:

Negative Feedback Amplifiers:    http://www.youtube.com/watch?v=gmSNPFXsalQ

3D Animation that shows the working of a Transistor: http://www.youtube.com/watch?v=IcrBqCFLHIY

Assignment    1

Last date for submission of assignment is 24-12-2018

1.   Explain how negative feedback acts on bandwidth, distortion, noise, input impedance and output impedance of a feedback amplifier. [April 2010], [December 2010]

2.  An amplifier has a mid band gain of 125 and a bandwidth 250 kHz. If 4% negative feedback is introduced, find the new bandwidth and gain. If the bandwidth is to be restricted to 1 MHz, find the feedback ratio.

3.  An amplifier has a mid-frequency gain of 100 and a bandwidth of 200 KHz.  1) What will be the new bandwidth and gain, if 5% negative feedback is introduced?  2) What should be the amount of feedback, if the bandwidth is to be restricted to 1 MHz? [April 2010]

4. An amplifier, without feedback, has a voltage gain of 400, lower cutoff frequency f₁ = 50 Hz, upper cutoff frequency f₂ = 200 KHz and a distortion of 10%. Determine the amplifier voltage gain, lower cutoff frequency and upper cutoff frequency and distortion, when a negative feedback is applied with feedback ratio of 0.01.

5. An amplifier, with feedback, has voltage gain of 100. When the gain without feedback changes by 20% and the gain with feedback should not vary more than 2%. If so, determine the values of open loop Gain A and feedback ratio β.

6. If an amplifier has a bandwidth of 300 kHz and a voltage gain of 100, what will be the new bandwidth and gain if 10% negative feedback introduced? What will be the gain-bandwidth product before and after feedback? What should be the amount of feedback if bandwidth is to be limited to 800 kHz?

7.  Explain voltage series and voltage shunt feedback connections.     [April 2010]

7. The voltage shunt feedback amplifier has the following values of circuit parameters. Rs = 600Ω; hie = 5kΩ; hfe = 80; RL = 2kΩ; RB = 40kΩ. Calculate Av; Rif ; Avf ; Rof and R′of.

8. With a neat circuit diagram, explain which type of feedback is employed in a BJT-emitter follower and obtain the expressions for A_V, A_I, R_i & R_o.

10. Transistors in the feedback amplifier shown below are identical and thin parameters are    h_ie = 1.1K, h_fe = 50, h_re= h_oe= 0. Identify the feedback amplifier and calculate A_vf, R_of and R_if.

      [November 2010]