An NPN-transistor circuit is arranged as shown in figure. It is
 

1. A common base amplifier circuit

2. A common emitter amplifier circuit

3. A common collector amplifier circuit

4. Neither of the above

For a transistor, the current amplification factor is 0.8 when it is connected in the common base configuration. The transistor is now connected in common emitter configuration. The change in the collector current when the base current changes by 6 mA, is:
1. 6 mA                       

2. 4.8 mA

3. 24 mA                     

4. 8 mA

In a common base amplifier circuit, calculate the change in base current if that in the emitter current is 2 mA and $\mathrm{\alpha }$ = 0.98

(1) 0.04 mA                           

(2) 1.96 mA

(3) 0.98 mA                           

(4) 2 mA

In a transistor circuit shown here the base current is 35 $\mu$A. The value of the resistor Rb is

1. 123.5 k$\mathrm{\Omega }$

2. 257 k$\mathrm{\Omega }$

3. 380.05 k$\mathrm{\Omega }$ 

4. None of these

For a transistor, in a common emitter arrangement, the alternating current gain $\mathrm{\beta }$ is given by

(1) $\mathrm{\beta }={\left(\frac{∆{\mathrm{I}}_{\mathrm{c}}}{∆{\mathrm{I}}_{\mathrm{B}}}\right)}_{{\mathrm{V}}_{\mathrm{C}}}$                       

(2) $\mathrm{\beta }={\left(\frac{∆{\mathrm{I}}_B}{∆{\mathrm{I}}_C}\right)}_{{\mathrm{V}}_{\mathrm{C}}}$

(3) $\mathrm{\beta }={\left(\frac{∆{\mathrm{I}}_{\mathrm{c}}}{∆{\mathrm{I}}_E}\right)}_{{\mathrm{V}}_{\mathrm{C}}}$                       

(4) $\mathrm{\beta }={\left(\frac{∆{\mathrm{I}}_E}{∆{\mathrm{I}}_C}\right)}_{{\mathrm{V}}_{\mathrm{C}}}$

The relation between $\mathrm{\alpha }$ and $\mathrm{\beta }$ parameters of current gains for a transistors is given by

(1) $\mathrm{\alpha }=\frac{\mathrm{\beta }}{1-\mathrm{\beta }}$               

(2) $\mathrm{\alpha }=\frac{\mathrm{\beta }}{1+\mathrm{\beta }}$

(3) $\mathrm{\alpha }=\frac{1-\mathrm{\beta }}{\mathrm{\beta }}$               

(4) $\mathrm{\alpha }=\frac{1+\mathrm{\beta }}{\mathrm{\beta }}$

In the CB mode of a transistor, when the collector emitter voltage is changed by 0.5 volt. The collector current changes by 0.05 mA. The output resistance will be 
(1) 10 k$\mathrm{\Omega }$                         

(2) 20 k$\mathrm{\Omega }$

(3) 5 k$\mathrm{\Omega }$                           

(4) 2.5 k$\mathrm{\Omega }$

Consider an NPN transistor amplifier in the common-emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current?
1. 1.1 mA                     

2. 1.01 mA

3. 0.01 mA                   

4. 10 mA

In a common base amplifier the phase difference between the input signal voltage and the output voltage is

(1) 0                     

(2) $\mathrm{\pi }/4$

(3)$\mathrm{\pi }/2$                  

(4) $\mathrm{\pi }$

In NPN transistor the collector current is 10 mA. If 90% of electrons emitted reach the collector, then

(1) Emitter current will be 9 mA

(2) Emitter current will be 11.1 mA

(3) Base current will be 0.1 mA

(4) Base current will be 0.01 mA