Exercise: Analog Electronics

Questions for: Analog Electronics

In a BJT amplifier the power gain from base to collector is 4000. The power gain in dB is
A:
3.6
B:
36
C:
7.2
D:
72
Answer: B

Gain in dB = 10 log (4000).

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An amplifier has open loop gain of 100, input impedance 1 kΩ and output impedance 100 Ω. If negative feedback with β = 0.99 is used, the new input and output impedances are
A:
10 Ω and 1 Ω
B:
10 Ω and 10 kΩ
C:
100 kΩ and 1 Ω
D:
100 kΩ and 10 Ω
Answer: C

Input impedance with feedback = (1 kΩ) (1 + 100 + 0.99) = 100 kΩ. Output impedance with feedback = .

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A CB amplifier has IE = 3.5 mA, a = 0.98 and RL = 600 Ω. The input impedance
A:
0.98 Ω
B:
0.025 Ω
C:
D:
600 Ω
Answer: C

. Input impedance of CB amplifier equals re .

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Leakage current approximately doubles for every 10°C increase in the temperature of a transistor has ICBO = 400 nA at 25°C, then its leakage current at 80°C
A:
10 μA
B:
18 μA
C:
20 μA
D:
15 μA
Answer: B

ICBO = (400 x 10-9) 2(80-25)/10 = 18 μA.

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A full wave diode rectifier using centre tapped transformer has diodes with forward resistance of 50 ohms each. The load resistance of 50 ohms each. The load resistance is also 50 ohms. The voltage regulation is
A:
20%
B:
50%
C:
100%
D:
200%
Answer: C

No load output voltage =

Output voltage at full load =

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