2 Amplification in the AC Domain 1. a. What is the expected amplification of a B

Question

2 Amplification in the AC Domain

1.

a. What is the expected amplification of a BJT transistor amplifier if the dc supply is set to zero volts?

b. What will happen to the output ac signal if the dc level is insufficient? Sketch the effect on the waveform.

c. What is the conversion efficiency of an amplifier in which the effective value of the current through a 2.2-kohms load is 5 mA and the drain on the 18-V dc supply is 3.8 mA?

4 The re Transistor Model

7.

Using the model of Fig. 16, determine the following for a common-emitter amplifier if B = 80, IE (dc) = 2 mA, and r0 = 40 kohms.

8.

The input impedance to a common-emitter transistor amplifier is 1.2 kohms with B = 140,ro = 50 kohms, and RL= 2.7 kohms. Determine:

a. re.

b. Ibif Vi = 30 mV.

c. Ic.

d. Ai=Io/Ii = IL/Ib.

e. Av= V0/Vi.

6 Voltage-Divider Bias

12.

For the network of Fig. 153:

a. Determine re.

b. Calculate Zi and Z0.

c. Find Av.

d. Repeat parts (b) and (c) with ro = 25 kohms.

Explanation / Answer

Ia.f the dc power supply is set to zero volts, the amplification will be zero

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b.Too low dc power level will result in a clipped output wave form

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c. P=i^2R = 5^2 2.2 =55 mW

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Pi= 68.4 Mw

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Nu= 55 mW/ 68.4 Mw = 0.804= 80.4%

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Zi= 10/0.5= 20 ohms

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V=0.98 x0.5 x1.3 =0.588v

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Av= 58.8

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Ai=0.98

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Ib= 10mu A

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