Transfer characteristic [output voltage $\left(V_{\mathrm{o}}\right)$ vs input voltage $\left(V_i\right)$] for a base biased transistor in CE configuration is as shown in the figure. For using transistor as a switch, it is used:
                     

1. in region III

2. both in region (I) and (III)

3. in region II

4. in region I

The figure shows a logic circuit with two inputs A and B and the output C.The voltage wave forms across A, B and C are as given.The logic circuit gate is 

1. OR gate                                          2. NOR gate

3. AND gate                                        4. NAND gate

The input resistance of a silicon transistor is

100 $\mathrm{\Omega }$. Base current is changed by 40 $\mathrm{\mu A}$

which results in a change in collector current

by 2 mA. This transistor is used as a common-

emitter amplifier with a load resistance of 4 k$\mathrm{\Omega }$.

The voltage gain of the amplifier is

1. 2000

2. 3000

3. 4000

4. 1000

Symbolic representation of four logic gates

are shown as

(i) 

(ii) 

(iii) 

(iv) 

Pick out which ones are for AND, NAND and 

NOT gates, respectively.

(a) (iii), (ii)and (i)

(b) (iii), (ii) and (iv)

(c) (ii), (iv) and (iii)

(d) (ii), (iii) and (iv)

If a small amount of antimony is added to germanium crystal

(1) the antimony becomes an acceptor atom

(2) there will be more free electrons than holes in the semiconductor

(3) its resistance is increased

(4) it becomes a p-type semiconductor

In forward biasing of the p-n junction 

The decreasing order of the wavelength of infrared, microwave, ultraviolet and gamma rays is

(1) gamma rays, ultraviolet, infrared, microwaves

(2) microwaves, gamma rays, infrared, ultraviolet

(3) infrared, microwave, ultraviolet, gamma rays

(4) microwave, infrared, ultraviolet, gamma rays

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

Pure Si at 500 K has equal number of electron $\left(n_{\mathit{e}}\right)$ and hole $\left(n_{\mathit{h}}\right)$ concentration of $1.5\times {10}^{\mathrm{16 }}{\mathrm{m}}^{-3}.$ Doping by indium increases $n_{\mathit{h}}$ to $4.5\times {10}^{22}$ ${\mathrm{m}}^{-3}.$ The doped semiconductor is of:

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