+2 PHYSICS UNIT 9. Semiconductor Devices And Their Applications

2.

In an N−type semiconductor, there are

immobile positive ions
Immobile negative ions
Holes as majority carriers
No minority carriers

Correct Answer

A. immobile positive ions

Explanation

In an N-type semiconductor, there are immobile positive ions. This is because N-type semiconductors are doped with impurities that introduce extra electrons into the crystal structure. These extra electrons are the majority carriers in N-type semiconductors, while the immobile positive ions are the result of the doping process. These positive ions do not contribute to the conductivity of the material and remain stationary within the crystal lattice.

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3.

The reverse saturation current in a PN junction diode is only due to

Minority carriers
Donor ions
Majority carriers
Acceptor ions

Correct Answer

A. Minority carriers

Explanation

The reverse saturation current in a PN junction diode is only due to minority carriers. In reverse bias, the majority carriers are pushed away from the junction, leaving behind a region depleted of majority carriers. This depletion region is populated by minority carriers, which are thermally generated. These minority carriers contribute to the reverse saturation current. Donor and acceptor ions do not directly contribute to the reverse saturation current, as they are involved in the formation of the depletion region and the forward bias behavior of the diode.

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4.

In the forward bias characteristic curve, a diode appears as

An ON switch
An OFF switch
A high resistance
A capacitor

Correct Answer

A. An ON switch

Explanation

In the forward bias characteristic curve, a diode appears as an ON switch because when the diode is forward biased, it allows current to flow easily through it, similar to how a switch is turned ON to allow the flow of electricity. This is in contrast to a diode in reverse bias, where it acts as an OFF switch and blocks the current flow.

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5.

Avalanche breakdown is primarily dependent on the phenomenon of

Collision
Recombination
Doping
Ionisation

Correct Answer

A. Collision

Explanation

Avalanche breakdown is primarily dependent on the phenomenon of collision. This is because avalanche breakdown occurs when a high electric field causes free electrons to gain enough energy to collide with other atoms or molecules in the material. These collisions then release more free electrons, creating a chain reaction that leads to a breakdown of the material's resistance. Therefore, collision is the key factor in initiating and sustaining the avalanche breakdown phenomenon.

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6.

The colour of light emitted by a LED depends on

Type of semiconductor material
The amount of forward current
Its forward bias
Its reverse bias

Correct Answer

A. Type of semiconductor material

Explanation

The colour of light emitted by a LED depends on the type of semiconductor material used. Different semiconductor materials have different energy band gaps, which determine the wavelength of light that can be emitted. For example, a semiconductor material with a smaller band gap will emit light with a higher energy and shorter wavelength, such as blue or violet light. On the other hand, a semiconductor material with a larger band gap will emit light with a lower energy and longer wavelength, such as red or infrared light. Therefore, the type of semiconductor material is the main factor that determines the colour of light emitted by a LED.

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7.

The emitter base junction of a given transistor is forward biased and its collector−base junction is reverse biased. If the base current is increased, then its

Ic will increase
Vcc will increase
Ic will decrease
VCE will increase

Correct Answer

A. Ic will increase

Explanation

When the emitter-base junction of a transistor is forward biased and the collector-base junction is reverse biased, increasing the base current will result in an increase in the collector current (Ic). This is because the forward biasing of the emitter-base junction allows for a larger number of charge carriers to flow from the emitter to the base, which in turn allows for a larger current to flow from the collector to the emitter. Therefore, an increase in the base current will lead to an increase in the collector current.

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8.

Improper biasing of a transistor circuit produces

Distortion in the output signal
Excessive heat at collector terminal
Faulty location of load line
Heavy loading of emitter current

Correct Answer

A. Distortion in the output signal

Explanation

Improper biasing of a transistor circuit refers to the incorrect setting of the operating point of the transistor. This can lead to distortion in the output signal, causing it to deviate from the original input signal. Distortion can manifest as changes in the shape, amplitude, or frequency content of the output signal. It occurs when the transistor is not properly biased to operate in its linear region, resulting in nonlinear behavior and signal distortion.

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9.

An oscillator is

An amplifier with feedback
A convertor of ac to dc energy
Nothing but an amplifier
An amplifier without feedback

Correct Answer

A. An amplifier with feedback

Explanation

An oscillator is an amplifier with feedback because it uses positive feedback to continuously generate and sustain an oscillating signal. The feedback loop in an oscillator allows a fraction of the output signal to be fed back to the input, reinforcing and regenerating the signal. This continuous feedback loop creates a sustained oscillation or periodic waveform at the desired frequency. Without feedback, an amplifier would not be able to generate and maintain the oscillating signal required for an oscillator.

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10.

Since the input impedance of an ideal operational amplifier is infinite,

Its input current is zero
Its output resistance is high
its output voltage becomes independent of load resistance
it becomes a current controlled device

Correct Answer

A. Its input current is zero

Explanation

An ideal operational amplifier has infinite input impedance, which means that it draws no current from the input source. This is because the input impedance is so high that it effectively acts as an open circuit, allowing no current to flow into the operational amplifier. Therefore, the input current of an ideal operational amplifier is zero.

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11.

If the output (Y) of the following circuit is 1, the inputs A B C must be

101
110
010
100

Correct Answer

A. 101

Explanation

If the output (Y) of the circuit is 1, it means that the circuit is in a state where it is producing a logical high output. In order for this to happen, the circuit must have a high input at position A, a low input at position B, and a high input at position C. Therefore, the inputs A, B, and C must be 101.

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12.

According to the laws of Boolean algebra, the expression (A + AB) is equal to

(4)
(3)
(2)
(1)

Correct Answer

A. (4)

Explanation

The expression (A + AB) can be simplified using the distributive property of Boolean algebra. By factoring out A, we get A(1 + B), which simplifies to A. Therefore, the expression (A + AB) is equal to A.

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13.

The Boolean expression ABC can be simplified as

(4)
(3)
(2)
(1)

Correct Answer

A. (4)

14.

In a Colpitt’s oscillator circuit

Capacitive feedback is used
Tapped coil is used
No tuned LC circuit is used
No capacitor is used

Correct Answer

A. Capacitive feedback is used

Explanation

In a Colpitt's oscillator circuit, capacitive feedback is used. This means that a capacitor is used to provide feedback from the output to the input of the circuit. This feedback helps to sustain oscillations by providing the necessary phase shift and amplification. It allows the circuit to generate a continuous oscillating signal without the need for a tuned LC circuit or a tapped coil.

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15.

Which semiconductor device is used primarily for amplifying or switching electronic signals in circuits?

Diode
Transistor
Resistor
Capacitor

Correct Answer

A. Transistor

Explanation

Transistors are semiconductor devices used to amplify or switch electronic signals and electrical power. Unlike diodes, which only allow current to pass in one direction, transistors can both amplify the input signal and act as switches. This makes them fundamental components in both analog and digital circuits, ranging from simple amplifiers to complex computer networks, confirming option B as the correct choice. Resistor and capacitor are not semiconductor devices but rather passive electronic components that respectively manage current flow and store electrical energy in an electrical field.

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0

+2 Physics Unit 9. Semiconductor Devices And Their Applications

The electrons in the atom of an element which determine its chemical and electrical properties are called

Quiz Preview

In an N−type semiconductor, there are

The reverse saturation current in a PN junction diode is only due to

In the forward bias characteristic curve, a diode appears as

Avalanche breakdown is primarily dependent on the phenomenon of

The colour of light emitted by a LED depends on

The emitter base junction of a given transistor is forward biased and its collector−base junction is reverse biased. If the base current is increased, then its

Improper biasing of a transistor circuit produces

An oscillator is

Since the input impedance of an ideal operational amplifier is infinite,

If the output (Y) of the following circuit is 1, the inputs A B C must be

According to the laws of Boolean algebra, the expression (A + AB) is equal to

The Boolean expression ABC can be simplified as

In a Colpitt’s oscillator circuit

Which semiconductor device is used primarily for amplifying or switching electronic signals in circuits?