Exercise: Analog Electronics

Questions for: Analog Electronics

An amplifier has input impedance of 4 kΩ and output impedance of 80 kΩ. It is used in negative feedback circuit with 10% feedback. If open loop gain is 90, the closed loop input and output impedances are
A:
40 kΩ and 8 kΩ respectively
B:
4 kΩ and 80 kΩ respectively
C:
0.4 kΩ and 800 kΩ respectively
D:
8 kΩ and 160 kΩ respectively
Answer: A

Closed loop input impedance = 4 (1 + 0.1 x 90) = 40 kΩ,

Closed loop Output impedance = = 8 kΩ.

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In a power amplifier the collector current flows for 270° of the input cycle. The operations is
A:
class A
B:
class B
C:
class AB
D:
class C
Answer: C

In class A operation IC exists for 360°. In class B operation IC exists for 180°. In between there is the class AB.

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A Ge diode operated at a junction temperature of 27°C. For a forward current of 10 mA, VD is found to be 0.3 V. If VD = 0.4 V then forward current will be
A:
400 mA
B:
475 mA
C:
477 mA
D:
480 mA
Answer: C

iD2 = (47.73) x 10 mA = 466 mA.

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A voltage tripler circuit and voltage quadrupler circuit use identical components. Then
A:
voltage regulation in both circuits will be same
B:
voltage regulation in both may or may not be same
C:
voltage regulation in quadrupler circuit will be better than in tripler circuit
D:
voltage regulation in quadrupler circuit will be poorer than in tripler circuit
Answer: D

Since voltage quadrupler circuit uses more components, voltage drop will be more and voltage regulation poorer.

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Which one of the following is connect expression of id for figure?
A:
B:
C:
0
D:
id1 - id2
Answer: A

iD = iD1 + iD2

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