In a CE transistor amplifier, the audio signal voltage across the collector resistance of 2kΩ is 2V. If the base resistance is 1kΩ and the current amplification of the transistor is 100, the input signal voltage is

0.1 V
1.0 V
1 mV
10 mV

Solution

Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is

0.75 A
zero
0.25 A
0.5 A

Solution

A zener diode, having breakdown voltage equal to 15V, is used in a voltage regulator circuit shown in figure. The current through the diode is

10 mA
15 mA
20 mA
5 mA

Solution

Pure Si at 500K has equal number of electron (n_e) and hole(n_h) concentrations of 1.5 × 10¹⁶ m^–3. Doping by indium increases n_h to 4.5 × 10²² m^–3. The doped semiconductor is of

n–type with electron concentration n_e= 5 × 10²² m^–3
p–type with electron concentration n_e= 2.5 × 10¹⁰ m^–3
n–type with electron concentration n_e= 2.5 × 10²³ m^–3
p–type having electron concentration n_e= 5 × 10⁹ m^–3

Solution

Symbolic representation of four logic gate are shown as

Pick out which ones are for AND, NAND and NOT gates,respectively

(ii), (iii) and (iv)
(iii), (ii) and (i)
(iii), (iii) and (iv)
(ii), (iv) and (iii)

A transistor is operated in common emitter configuration at V_C= 2V such that a change in the base current from 100 μA to 300 μA produces a change in the collector current from 10mA to 20 mA. The current gain is

Solution

The following figure shows a logic gate circuit with two inputs A and B and the output Y. The voltage wave forms of A, Band Y are given

The logic gate is :

NAND gate
NOR gate
OR gate
AND gate

Solution

From the given wave forms, the truth table is as follows.

The above truth table is for NAND gate.Therefore,the logic gate is NAND gate.

For transistor action

(1)Base, emitter and collector regions should have similar size and doping concentrations.

(2)The base region must be very thin and lightly doped.

(3)The eimtter-base junction is forward biased and base-collector junction is reverse based.

(4)Both the emitter-base junction as well as the base-collector junction are forward biased.

(3) and(4)
(4) and(1)
(1) and(2)
(2) and (3)

Solution

For transistor action,the base region must be very thin and lightly doped. Also, the emitter-base junction is forward biased and base-collector junction is reverse biased.

A common emitter amplifier has a voltage gain of 50, an inputimpedance of 100Ω and an output impedance of 200Ω.The power gain of the amplifier is

500
1000
1250
50

Solution

Which one of the following statement is false ?

Pure Si doped with trivalent impurities gives a p-type semiconductor
Majority carriers in a n-type semiconductor are holes
Minority carriers in a p-type semiconductor are electrons
The resistance of intrinsic semiconductor decreases with increase of temperature

Solution

Majority carriers in an n-type semiconductor are electrons.

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