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.  III and IV only

2.  I and III only

3.  II only

4.  II and IV only

A Zener diode, having breakdown voltage equal to \(15\) V, is used in a voltage regulator circuit, as 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:

Which of the following pairs of statements is correct?
1. (d) and (a)
2. (a) and (b)
3. (b) and (c)                                       
4. (c) and (d)

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 

(1) $6000 \stackrel{\circ }{\mathrm{A}}$                                   
(2) $4000 \mathrm{nm}$
(3) $6000 \mathrm{nm}$                                 
(4) $4000 \stackrel{\circ }{\mathrm{A}}$

The circuit is equivalent to

1. AND gate                              2. NAND gate

3. NOR gate                              4. OR gate 

In the forward bias arrangement of a PN-junction diode

(1) The N-end is connected to the positive terminal of the battery

(2) The P-end is connected to the positive terminal of the battery

(3) The direction of current is from N-end to P-end in the diode

(4) The P-end is connected to the negative terminal of battery