Q1.A p n junction has a built-in potential of 0.8 V. The depletion layer width a
reverse bias of 1.2 V is 2 μm. For a reverse bias of 7.2 V, the depletion layer
width will be
Q2.Group I lists four types of p − n junction diodes. Match each device in Group I with one of the option in Group II to indicate the bias condition of the device in its normal mode of operation.
Group - I Group-II
(P) Zener Diode (1) Forward bias
(Q) Solar cell (2) Reverse bias
(R) LASER diode
(S) Avalanche Photodiode
Answer : Option BExplaination / Solution:
Zener diode and Avalanche diode works in the reverse bias and laser diode works in forward bias.
In solar cell diode works in forward bias but photo current is in reverse direction. Thus
Zener diode : Reverse Bias
Solar Cell : Forward Bias
Laser Diode : Forward Bias
Avalanche Photo diode : Reverse Bias
Group I lists four different semiconductor devices. match each device in Group I with its charactecteristic property in Group II
Group-I Group-II
(P) BJT (1) Population iniversion
(Q) MOS capacitor (2) Pinch-off voltage
(R) LASER diode (3) Early effect
(S) JFET (4) Flat-band voltage
Answer : Option CExplaination / Solution:
In BJT as the B-C reverse bias voltage increases, the B-C space charge region
width increases which xB (i.e. neutral base width) > A change in neutral base
width will change the collector current. A reduction in base width will causes
the gradient in minority carrier concentration to increase, which in turn causes
an increased in the diffusion current. This effect si known as base modulation as
early effect.
In JFET the gate to source voltage that must be applied to achieve pinch off
voltage is described as pinch off voltage and is also called as turn voltage or
threshold voltage.
In LASER population inversion occurs on the condition when concentration of
electrons in one energy state is greater than that in lower energy state, i.e. a non
equilibrium condition.
In MOS capacitor, flat band voltage is the gate voltage that must be applied to
create flat ban condition in which there is no space charge region in semiconductor
under oxide.
Q7.The figure shows the high-frequency capacitance - voltage characteristics of Metal/Sio2/silicon (MOS) capacitor having an area of 1 × 10-4 cm2. Assume that the permittivities (ε0εr) of silicon and Sio are 1 × 10-12F/cm and 3.5 × 10-13F/ cm respectively.
Q8.The figure shows the high-frequency capacitance - voltage characteristics of Metal/Sio2/silicon (MOS) capacitor having an area of 1 × 10-4 cm2. Assume that the permittivities (ε0εr) of silicon and Sio are 1 × 10-12F/cm and 3.5 × 10-13F/ cm respectively.
The figure shows the high-frequency capacitance - voltage characteristics of Metal/Sio2/silicon (MOS) capacitor having an area of 1 × 10-4 cm2. Assume that the permittivities (ε0εr) of silicon and Sio are 1 × 10-12F/cm and 3.5 × 10-13F/ cm respectively.
Consider the following statements about the C − V characteristics plot :
S1 : The MOS capacitor has as n-type substrate
S2 : If positive charges are introduced in the oxide, the C − V polt will shift to the left.
Then which of the following is true?
Answer : Option CExplaination / Solution:
Depletion region will not be formed if the MOS capacitor has n type substrate but from C-V characteristics, C reduces if V is increased. Thus depletion region must be formed. Hence S1 is false
If positive charges is introduced in the oxide layer, then to equalize the effect the applied voltage V must be reduced. Thus the C − V plot moves to the left. Hence S2 is true.
Q10.Which of the following is NOT associated with a p - n junction ?
Answer : Option DExplaination / Solution:
Channel length modulation is not associated with a p - n junction. It is being associated with MOSFET in which effective channel length decreases, producing the phenomenon called channel length modulation.
Total Question/Mark :
Scored Mark :
Mark for Correct Answer : 1
Mark for Wrong Answer : -0.5
Mark for Left Answer : 0