31 Year NEET Previous Year Questions: Semiconductor Electronics - 4
25 Questions MCQ Test Physics Class 12 | 31 Year NEET Previous Year Questions: Semiconductor Electronics - 4
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p-n junction is said to be forward biased, when [1988]
For forward biasing of p-n junction, the
positive terminal of external battery is to be
connected to p-semiconductor and negative
terminal of battery to the n-semiconductor.
At absolute zero, Si acts as [1988]
Semiconductors are insulators at room
temperature
When n-type semiconductor is heated [1989]
Due to heating, when a free electron is
produced then simultaneously a hole is also
produced.
Radiowaves of constant amplitude can begenerated with [1989]
Radiowaves of constant amplitude can be
produced by using oscillator with proper
feedback.
In a common base amplifier the phase differencebetween the input signal voltage and the outputvoltage is [1990]
The phase difference between output
voltage and input signal voltage in common
base transistor or circuit is zero.
When a triode is used as an amplifier the phasedifference between the input signal voltage andthe output is [1990]
Voltage gain of an amplifier
The negative sign indicates that the output
voltage differs in phase from the input
voltage by 180°(or π). This holds for a pure
resistive load.
The depletion layer in the p-n junction region iscaused by [1991]
The depletion layer in the p-n junction region
is caused by diffusion of charge carriers.
The following truth table corresponds to the logic gate [1991]
This truth table is of identity, X = A + B, hence
OR gate.
To use a transistor as an amplifier [1991]
To use a transistor as an amplifier the emitter
base junction is forward biased while the
collector base junction is reverse biased
Which one of the following is the weakest kindof bonding in solids [1992]
Vander Waal’s bonding is the weakest
bonding in solids
For amplification by a triode, the signal to beamplified is given to [1992]
The amplifying action of a triode is based on
the fact that a small change in grid voltage
causes a large change in plate current. The
AC input signal which is to be amplified is
superimposed on the grid potential.
For an electronic valve, the plate current I andplate voltage V in the space charge limited regionare related as [1992]
According to Child’s Law,
A piece of copper and other of germanium arecooled from the room temperature to 80 K, then [1993]
Copper is a conductor, so, its resistance
decreases on decreasing temperature as
thermal agitation decreases whereas
germanium is semiconductor, therefore, on
decreasing temperature resistance increases.
Diamond is very hard because [1993]
Diamond is very hard due to large cohesive
energy.
The part of the transistor which is heavily dopedto produce large number of majority carriers is [1993]
The function of emitter is to supply the
majority carriers. So, it is heavily doped
An oscillator is nothing but an amplifer with [1994]
A positive feed back from output to input in
an amplifier provides oscillations of constant
amplitude.
When a p-n junction diode is reverse biased theflow of current across the junction is mainly dueto [1994]
When p-n junction is reverse biased, the flow
of current is due to drifting of minority charge
carriers across the junction.
In Fig., the input is across the terminals A and C and the output is across B and D. Then the output is
It is the circuit of full wave rectifier.
Which of the following gates corresponds tothe truth table given below? [1994]
This truth table is of the identity, 
hence it is NAND gate.
Here, the output is high even if all inputs are low or one input is low.
In the diagram, the input is across the terminals A and C and the output is across B and D. Then the output is [1994, 02]
The given circuit is a circuit of full wave
rectifier.
Which of the following, when added as animpurity, into the silicon, produces n-type semiconductor? [1995]
Phosphorous (P) is pentavalent and silicon
is tetravalent. Therefore, when silicon is
doped with pentavalent impurity, it forms a
n-type semiconductor.
The current gain for a transistor working ascommon-base amplifier is 0.96. If the emittercurrent is 7.2 mA, then the base current is [1996]
Current gain (α) = 0.96
When an n–p–n transistor is used as an amplifierthen [1996]
In an n-p-n transistor, the charge carriers,
are free electrons in the transistor as well as
in external circuit; these electrons flow from
emitter to collector
When arsenic is added as an impurity to silicon,the resulting material is [1996]
Arsenic contains 5 electrons in its outermost
shell. When Arsenic is mixed with silicon
there is one electron extra in silicon crystal.
Hence, such type of semi conductor is ntype
semi conductor
To obtain a p-type germanium semiconductor,it must be doped with [1997]
p-type germanium semiconductor is formed
when it is doped with a trivalent impurity
atom.
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