Semiconductor Devices and Circuits Quiz

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Questions and Answers

How does increasing the doping concentration in a semiconductor impact the width of the depletion region in a p-n junction under reverse bias?

It leaves the depletion region unaffected because the applied voltage is the determining factor.

It causes the depletion region to oscillate in width due to the dynamic equilibrium of charge carriers.

It narrows the depletion region as more charge carriers are available to neutralize the region.

It widens the depletion region due to the increased number of ionized impurities. (correct)

What limitation primarily restricts the maximum electron emission current in thermionic emission?

Space charge effects near the cathode surface counteract further electron emission. (correct)

The crystal structure of the metal degrades at high temperatures, impeding electron release.

The work function of the emitting material rapidly increases with temperature.

The anode voltage drops significantly due to increased electron flow.

What implication does the Fermi level's position have on the conductivity of an intrinsic semiconductor as temperature increases?

As temperature increases, the Fermi level shifts closer to the conduction band, increasing conductivity.

As temperature increases, the position of the Fermi level dictates the type of majority charge carriers.

As temperature increases, the Fermi level remains fixed, but the band gap widens, decreasing conductivity.

As temperature increases, the Fermi level shifts towards the center of the band gap, and conductivity increases exponentially. (correct)

How is the Early effect manifested in a bipolar junction transistor's behavior?

An increase in the collector current due to the reduced effective base width with increasing collector voltage. (C) Signup and view all the answers

What characteristic of the tungsten target material is most crucial for efficient X-ray production, and why?

High melting point to withstand the intense heat from electron bombardment. (C) Signup and view all the answers

In a CRO, if the input signal frequency is an exact multiple of the time base frequency, what display pattern is typically observed, and why?

A stable, single-cycle waveform because the signal retraces itself perfectly. (C) Signup and view all the answers

In a half-wave rectifier circuit, what is the effect of increasing the value of the filter capacitor on the output DC voltage and ripple factor?

Increases the DC voltage and decreases the ripple factor due to improved filtering. (C) Signup and view all the answers

How does the base-width modulation (Early effect) in a BJT affect the transistor's output characteristics in the active region?

It leads to a decrease in the output resistance, making the collector current slightly dependent on the collector-emitter voltage. (B) Signup and view all the answers

How does increasing the frequency of the input signal affect a full-wave rectifier's output?

It increases the ripple frequency but does not affect the average DC voltage. (B) Signup and view all the answers

What is the consequence of applying an excessively large reverse bias voltage to a p–n junction?

The junction undergoes avalanche breakdown, leading to a sudden surge in reverse current. (B) Signup and view all the answers

Why is phosphorus preferred over aluminum as a dopant for silicon in manufacturing semiconductors for specific applications?

Phosphorus contributes free electrons, increasing conductivity in n-type semiconductors. (D) Signup and view all the answers

What is the key factor that limits the high-frequency performance of a thermionic diode?

The transit time of electrons between the cathode and anode. (C) Signup and view all the answers

How can NAND gates be configured to create an equivalent XOR gate?

Four NAND gates configured with a specific interconnection pattern can implement an XOR gate. (B) Signup and view all the answers

How might increasing the value of the base resistor ($R_B$) in a transistor amplifier circuit impact the amplifier's performance?

It reduces the base current, potentially leading to cutoff or increased distortion. (A) Signup and view all the answers

What is the effect of increasing the capacitance value in a capacitor-filtered rectifier circuit?

It decreases the ripple voltage and increases the average DC output voltage. (C) Signup and view all the answers

What specific property of tungsten makes it ideal for use as the anode material in X-ray tubes that involve high-energy electron collisions?

Tungsten’s high atomic number enhances the efficiency of bremsstrahlung radiation production. (A) Signup and view all the answers

What is the practical implication if the current gain ($h_{fe}$) of a transistor varies significantly with temperature?

The transistor may experience thermal runaway, leading to potential failure. (D) Signup and view all the answers

How can a resistor be utilized in series with an LED to prevent damage?

To limit the current flowing through the LED, preventing burnout. (D) Signup and view all the answers

Flashcards

Depletion Zone in Forward Bias

The depletion zone narrows and allows current to flow when a p-n junction is forward biased.

Thermionic Emission

Thermionic emission is the emission of electrons from a heated metal surface.

Semiconductor Resistance with Temperature

The resistance of a pure semiconductor decreases as temperature increases, generating more charge carriers.

Collector Current in Transistor

If the base current in an n-p-n transistor is increased, the collector current increases significantly.