A transistor is operated in common emitter configuration at ${\mathrm{V}}_{\mathrm{C}}=2 \mathrm{V}$ such that a change in the base current from $100 \mathrm{\mu A}$ to $300 \mathrm{\mu A}$ produces a change in the collector current from $10 \mathrm{mA}$ to $20 \mathrm{mA}$. The current gain is 

1. 75                                               2. 100

3. 25                                                4. 50

In the following figure, the diodes which are forward biased, are

(1) C and D only

(2) A and C only

(3) B only

(4) Band D only

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

1. 10 mA                                                    2. 15 mA

3. 20 mA                                                     4. 5 mA

Which one of the following statement is false?

(1) Pure Si doped with trivalent impurities gives a p-type semiconductor 

(2) Majority carries in a n-type semiconductor are holes

(3) Minority carries in a p-type semiconductor are electrons

(4) The resistance of intrinsic semiconductor decreases with increase of temperature 

To get an output Y =1 from the circuit shown below, the input must be

        A     B     C

(1)   0      1     0

(2)   0      0     1

(3)   1      0     1

(4)   1      0     0

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

The logic gate is 

(1) $\mathrm{NOR}$ gate                                                 

(2) $\mathrm{OR}$ gate

(3) $\mathrm{AND}$ gate                                                 

(4) $\mathrm{NAND}$gate

For transistor action

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

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

(3) The emitter-base junction is forward biased and the base-collector junction is reverse biased.

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

Which of the following pairs of statements is correct?

(a)   (4) and (1)                                       (b)   (1) and (2)

(c)   (2) and (3)                                       (d)    (3) and (4)

A p-n photodiode is fabricated from a semiconductor with a band gap of $2.5 \mathrm{eV}.$ It can detect a signal of wavelength 

(a) $6000 \stackrel{\circ }{\mathrm{A}}$                                    (b) $4000 \mathrm{nm}$

(c) $6000 \mathrm{nm}$                                  (d) $4000 \stackrel{\circ }{\mathrm{A}}$

The circuit is equivalent to

1. AND gate                              2. NAND gate

3. NOR gate                              4. OR gate 

The electrical circuit used to get smooth output from a rectifier circuit is called 

(1) Oscillator                         

(2) Filter

(3) Amplifier                           

(4) Logic gates