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Electronics and Communication Engineering - Analog Electronics

Exercise : Analog Electronics - Section 2
16.
In figure, transistor βdc = 100 and LED voltage when it is conducting is 2 V. Then the base current which saturates the transistor is
18 mA
1.8 mA
0.18 mA
0.018 mA
Answer: Option
Explanation:

.

17.
In figure the dc emitter current of each transistor is about
4 mA
2 mA
3 mA
1 mA
Answer: Option
Explanation:

Total . It divides equally between the two transistors.

18.
The input voltage for starting oscillations in an oscillator is caused by
negative feedback
positive feedback
noise voltage in resistors
a special generator
Answer: Option
Explanation:

The amplifier in the oscillator amplifies the noise voltages. However phase shift around the closed loop is zero at only one frequency. Therefore, only this frequency appears at output.

19.
The current flowing in a certain P-N junction at room temperature is 2 x 10-7 Amp. When a large reverse biased voltage is applied. Calculate the current flowing when 0.1 volts is applied.
9 μA
10 μA
2 μA
4 μA
Answer: Option
Explanation:

20.
In following figure find VDSQ by assuming gate current is negligible for the p-channel JFET. (if IDQ = - 6 mA, RS = 0, VDD = -18 V, RD = 2 kΩ, IDSS = - 10 mA, IPO = - 3 V)
4 V
- 6 V
- 10 V
6 V
Answer: Option
Explanation:

By Appling KVL around drain source loop.

VDSQ = -18 - (-6). 2 x 103 = - 18 + 12 k x 10-3 -6 V.

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