### Eamcet - Physics - Semiconductor Physics

In n-p-n transistor, in CE configuration:(1)  The emitter is heavily doped than the collector.(2)  Emitter and collector can be interchanged.(3)  The base region is very thin but is heavily doped.(4)  The conventional current flows from base to emitter

A.  (1) and (2) are correct

B.  (1) and (3) are correct

C.  (1) and (4) are correct

D.   (2) and (3) are correct

An n-p-n transistor power amplifier in C-E configuration gives :

A.  voltage amplification only

B.  currents amplification only

C.  both current and voltage amplifications

D.  only power gain of unity

To obtain p-type extrinsic semi- conductor, the impurity element to be added to Germanium should be of valency :

A.  2

B.  3

C.  4

D.  5

In an n-type semiconductor, the Fermi energy level lies

A.  in the forbidden energy gap nearer to the conduction band

B.  in the forbidden energy gap nearer to the valence band

C.  in the middle of forbidden energy gap

D.  outside the forbidden energy gap

Consider a p-n junction as a capacitor, formed with p nnd n-materials acting as thin metal electrodes and depletion layer width acting as separation between them. Basing on this, assume that a n-p-n transistor is working as an amplifier in CE configuration. If C1 and C2 are the base-emitter and collector-emitter junction capacitances , then :

A.  C1 > C2

B.  C1 < C2

C.  C1 = C2

D.  C1 = C2 = 0

A transistor having a β equal to 80 has a change in base current of 250μA,then the change in collector current is :

A.  20,000 mA

B.  200 mA

C.  2000 mA

D.  20 mA

Indium impurity in germanium makes it into a

A.  n-type semiconductor

B.  p-type semiconductor

C.  insulator

D.  intrinsic semiconductor

While a collector to emitter voltage is constant in a transistor, the collector current changes by 8.2 mA. When the emitter current changes by 8.3 mA. The value of forward current ratio is:

A.  82

B.  83

C.  8.2

D.  8.3

Which of the following Statements is not correct when a junction diode is in forward bias ?

A.  The width of depletion region decreases

B.  Tree electrons on n-side will move towards the junction

C.  Holes on p-side move towards the junction

D.  Electrons on n-side and holes on p-side will move away from junction

In a transistor if IC/IE and IC/IB=β.If α varies between 20/21 and 100/101,then the value of β lies between

A.  1-10

B.  0.95-0.99

C.  20-100

D.  200-300