Bjt Exercise

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  • Topic: Electronic amplifier, Common emitter, Cascode
  • Pages : 4 (477 words )
  • Download(s) : 899
  • Published : December 9, 2010
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Determine VCB in the transistor circuit shown in Figure 1. The transistor is made of silicon and has =150. Assume VCE = 0.7 V.

Figure 1

Ans:2.85 V
(4 marks)

Determine the voltage gain, Av of the circuit shown in Figure 2. Assume = 200.

Figure 2
Ans:Av = 291
(6 marks)

For the common emitter amplifier circuit shown in Figure 3,

(i) Draw the h parameter equivalent circuit.
(ii) Derive the expression for voltage gain and input impedance in h parameters. (iii) If the transistor of Figure 3 has the following set of h parameters: hie = 2k; hfe = 100; hre = 5 × 10-4; hoe = 2.5 × 10-5 S

Find the voltage gain and ac input impedance.

Figure 3

Ans:Zin = 1.53k,Av = 375
(10 marks)

Consider the circuit in Figure 4 below. Find the voltage gain of the amplifier.

Figure 4
(8 marks)

If CE were to be removed from the circuit in Figure 4, what would be the voltage gain? What do you conclude from the result of this calculation?

Ans:5.38. CE increases the voltage gain from 5.38 to 360.
(2 marks)

Explain the operation of a transistor as an amplifier. |
(5 marks)|

For the common emitter amplifier shown in Figure 5, determine the following:

(i) internal emitter resistance, re’
(ii) input impedance , Zi
(iii) voltage gain, Av

Figure 5

Ans:r’e = 30.56 ,Zi = 1/768 k, Av = 127.6
(10 marks)

Draw the generalized h-parameter equivalent circuit for the bipolar junction transistor connected in the common-emitter configuration.


(5 marks)

Give the equations relating the terminal variables Vi, Vo, IB, and IC in terms of the h-parameters for the transistor connected in the common-emitter configuration shown in Figure 6.

Figure 6


(4 marks)

The transistor used in the common-emitter amplifier of Figure 7 has the following hybrid parameter values:

hie 1.5 kΩ,hfe 100,hoe 100 μS,hre 0.

Draw the small signal h-parameter...
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