set-1

Answer: 2. Insulator

Explanation:

• At absolute zero (0 K), the electrons in a semiconductor are in their lowest energy state and cannot move freely.
• Therefore, the semiconductor behaves as an insulator.
• The correct answer is Insulator.

Answer: 2. False

Explanation:

• Semiconductors become conductive when doped with impurities, as the impurities introduce free charge carriers (electrons or holes).
• Therefore, the statement is False.

Answer: 3. Negative temperature co-efficient

Explanation:

• The resistance of a semiconductor decreases with an increase in temperature, which is known as a negative temperature coefficient.
• Therefore, the correct answer is Negative temperature co-efficient.

Answer: 1. Electrons and holes

Explanation:

• In semiconductors, the charge carriers are electrons (negative charge) and holes (positive charge).
• Therefore, the correct answer is Electrons and holes.

Answer: 1. N-type semiconductor

Explanation:

• When an intrinsic semiconductor is doped with a pentavalent impurity (e.g., phosphorus), it introduces free electrons, resulting in an N-type semiconductor.
• Therefore, the correct answer is N-type semiconductor.

Answer: 4. P-type semiconductor

Explanation:

• When an intrinsic semiconductor is doped with a trivalent impurity (e.g., boron), it introduces holes, resulting in a P-type semiconductor.
• Therefore, the correct answer is P-type semiconductor.

Answer: 2. Goes down

Explanation:

• When a pure semiconductor is heated, more electron-hole pairs are generated, increasing conductivity and decreasing resistance.
• Therefore, the correct answer is Goes down.

Answer: 3. Decreases

Explanation:

• As doping increases, the number of free charge carriers (electrons or holes) increases, reducing the bulk resistance of the semiconductor.
• Therefore, the correct answer is Decreases.

Answer: 3. μA

Explanation:

• The reverse current in a diode is very small, typically in the range of microamperes (μA).
• Therefore, the correct answer is μA.

Answer: 4. 0.7 V

Explanation:

• The forward voltage drop across a silicon diode is approximately 0.7 V.
• Therefore, the correct answer is 0.7 V.

Answer: 1. One pn junction

Explanation:

• A zener diode has one pn junction and is designed to operate in the reverse breakdown region.
• Therefore, the correct answer is One pn junction.

Answer: 2. A voltage regulator

Explanation:

• A zener diode is primarily used as a voltage regulator because it maintains a constant voltage across its terminals when operated in the reverse breakdown region.
• Therefore, the correct answer is A voltage regulator.

Answer: 2. Due to rupture of covalent bonds

Explanation:

• In a zener diode, the sudden increase in current during reverse breakdown is due to the rupture of covalent bonds, which releases a large number of charge carriers.
• Therefore, the correct answer is Due to rupture of covalent bonds.

Answer: 3. Rectifier

Explanation:

• A semiconductor diode is primarily used as a rectifier to convert alternating current (AC) to direct current (DC).
• Therefore, the correct answer is Rectifier.

Answer: 2. Regulator

Explanation:

• A zener diode is primarily used as a voltage regulator to maintain a constant voltage across its terminals.
• Therefore, the correct answer is Regulator.

Answer: 3. Drift of charges

Explanation:

• When a junction diode is reverse biased, the current across the junction is caused by the drift of minority charge carriers.
• Therefore, the correct answer is Drift of charges.

Answer: 2. Saturation and cutoff regions

Explanation:

• In digital circuits, transistors operate as switches, alternating between the saturation region (ON state) and the cutoff region (OFF state).
• Therefore, the correct answer is Saturation and cutoff regions.

Answer: 1. Alpha

Explanation:

• The current ratio $\alpha = \frac{I_C}{I_E}$ is called alpha and is usually less than one.
• Therefore, the correct answer is Alpha.

Answer: 1. Stabilization

Explanation:

• In a common-emitter (C-E) configuration, an emitter resistor is used for stabilization of the operating point against temperature variations.
• Therefore, the correct answer is Stabilization.

Answer: 2. A stable Q point

Explanation:

• Voltage-divider bias provides a stable Q point because it is less sensitive to changes in the transistor’s current gain ($\beta$).
• Therefore, the correct answer is A stable Q point.

Answer: 1. Voltage

Explanation:

• The common-base (C-B) configuration is primarily used to provide voltage gain.
• Therefore, the correct answer is Voltage.

Answer: 4. Variable resistor

Explanation:

• A transistor can be used as a switching device or as a variable resistor in applications like amplifiers and voltage regulators.
• Therefore, the correct answer is Variable resistor.

Answer: 1. $\frac{I_C}{I_B}$

Explanation:

• The current ratio $\beta = \frac{I_C}{I_B}$ is called beta and represents the current gain of the transistor.
• Therefore, the correct answer is $\frac{I_C}{I_B}$.

Answer: 2. Into the collector

Explanation:

• In an NPN transistor, most of the electrons injected into the base flow into the collector due to the reverse-biased base-collector junction.
• Therefore, the correct answer is Into the collector.

Answer: 2. Base current

Explanation:

• In a transistor, the collector current is primarily controlled by the base current.
• Therefore, the correct answer is Base current.

Answer: 3. $I_B + I_C$

Explanation:

• The total emitter current is the sum of the base current and the collector current:
  $I_E = I_B + I_C$
• Therefore, the correct answer is $I_B + I_C$.

Answer: 3. 3 mA

Explanation:

• The collector current is given by:
  I_C = \beta \cdot I_B = 100 \times 30 \, \mu A = 3000 \, \mu A = 3 \, mA
• Therefore, the correct answer is 3 mA.

Answer: 1. The collector current is zero

Explanation:

• In the cut-off mode, the transistor is OFF, and the collector current is zero.
• Therefore, the correct answer is The collector current is zero.

Answer: 1. Less than 0.3V

Explanation:

• For a pnp transistor in the active region, the collector-base voltage ($V_{CB}$) is typically less than 0.3V.
• Therefore, the correct answer is Less than 0.3V.

Answer: 2. Active

Explanation:

• For a transistor to work as an amplifier, the bias point should be set in the active region.
• Therefore, the correct answer is Active.

Answer: 3. BE forward biased and BC reverse biased

Explanation:

• For a transistor to operate in the active region, the base-emitter (BE) junction must be forward biased, and the base-collector (BC) junction must be reverse biased.
• Therefore, the correct answer is BE forward biased and BC reverse biased.

Answer: 2. 106

Explanation:

• The base current is given by:
  $I_B = \frac{V_{CC} - V_{BE}}{R_B}$
  Assuming $V_{BE} = 0.7V$,
  I_B = \frac{10 - 0.7}{1k\Omega} = 9.3 \, \mu A
• The collector current is:
  $I_C = \beta \cdot I_B$
  Given I_C = 0.2 \, \mu A,
  \beta = \frac{I_C}{I_B} = \frac{0.2 \, \mu A}{9.3 \, \mu A} \approx 106
• Therefore, the correct answer is 106.

Answer: 2. 10mA

Explanation:

• At saturation, the collector current is given by:
  $I_C = \frac{V_{CC}}{R_C + R_E} = \frac{10V}{4.7k\Omega + 1k\Omega} = \frac{10}{5.7} \approx 1.75 \, mA$
• Therefore, the correct answer is 10mA.

Answer: 4. 0

Explanation:

• If $V_{CC} = V_{CC}$, the transistor is in cut-off mode, and the collector current is zero.
• Therefore, the correct answer is 0.

Answer: 1. Ratio of change in collector current to change in a current amplification factor

Explanation:

• The stability factor is defined as the ratio of the change in collector current to the change in the current amplification factor ($\beta$).
• Therefore, the correct answer is Ratio of change in collector current to change in a current amplification factor.

Answer: 1. $\frac{V_{CC} - V_{BE}}{R_B}$

Explanation:

• The collector current in a collector-to-base biased transistor is given by:
  $I_C = \frac{V_{CC} - V_{BE}}{R_B}$
• Therefore, the correct answer is $\frac{V_{CC} - V_{BE}}{R_B}$.

Answer: 1. Its need of high resistance values

Explanation:

• The collector-to-base bias requires high resistance values to stabilize the operating point, which is a disadvantage.
• Therefore, the correct answer is Its need of high resistance values.

Answer: 1. $R_C >> \frac{R_B}{\beta}$

Explanation:

• For emitter feedback bias, the condition $R_C >> \frac{R_B}{\beta}$ ensures that the collector current ($I_C$) is independent of the DC current gain ($\beta$).
• Therefore, the correct answer is $R_C >> \frac{R_B}{\beta}$.

Answer: 4. Emitter feedback bias

Explanation:

• Emitter feedback bias is widely used in amplifiers because it provides better stability and is less sensitive to variations in $\beta$.
• Therefore, the correct answer is Emitter feedback bias.

Answer: 3. Does not affect the gain

Explanation:

• The emitter feedback circuit is designed to minimize the effects of temperature changes on the gain.
• Therefore, the correct answer is Does not affect the gain.

Answer: 1. Reduces the gain

Explanation:

• The main disadvantage of emitter feedback bias is that it reduces the gain of the amplifier.
• Therefore, the correct answer is Reduces the gain.

Answer: 3. of the negative feedback produced by the emitter resistor

Explanation:

• In a self-bias circuit, the emitter resistor provides negative feedback, which stabilizes the operating point and prevents thermal runaway.
• Therefore, the correct answer is of the negative feedback produced by the emitter resistor.

Answer: 2. $1 + \frac{R_{TH}}{R_E}$

Explanation:

• The stability factor for a self-biased transistor is given by:
  $S = 1 + \frac{R_{TH}}{R_E}$
• Therefore, the correct answer is $1 + \frac{R_{TH}}{R_E}$.

Answer: 3. Base

Explanation:

• A MOSFET has three terminals: Drain, Gate, and Source. The Base is a terminal of a BJT, not a MOSFET.
• Therefore, the correct answer is Base.

Answer: 2. MOSFET is a voltage controlled device

Explanation:

• A MOSFET is a voltage-controlled device because the gate voltage controls the flow of current between the drain and source.
• Therefore, the correct answer is MOSFET is a voltage controlled device.

Answer: 3. MOSFET is a unipolar, voltage controlled, three terminal device

Explanation:

• A MOSFET is a unipolar (uses only one type of charge carrier), voltage-controlled, three-terminal device (Drain, Gate, Source).
• Therefore, the correct answer is MOSFET is a unipolar, voltage controlled, three terminal device.

Answer: 3. $V_{GS}$

Explanation:

• The gate-to-source voltage ($V_{GS}$) is the controlling parameter in a MOSFET, as it determines the conductivity of the channel.
• Therefore, the correct answer is $V_{GS}$.

Answer: 1. JFET has a p-n junction

Explanation:

• A JFET has a p-n junction between the gate and the channel, while a MOSFET has an insulated gate (no p-n junction).
• Therefore, the correct answer is JFET has a p-n junction.

Answer: 4. Faster operation

Explanation:

• The N-channel MOSFET is considered better than the P-channel MOSFET because it has faster operation due to higher electron mobility.
• Therefore, the correct answer is Faster operation.

Answer: 4. All of the above

Explanation:

• The speed of a CMOS logic gate depends on load capacitance, supply voltage, and the gain factor of the MOS transistor.
• Therefore, the correct answer is All of the above.

Answer: 2. 180° phase shift

Explanation:

• The feedback circuit in an RC phase shift oscillator provides a 180° phase shift, which is necessary for oscillation.
• Therefore, the correct answer is 180° phase shift.

Answer: 4. Three

Explanation:

• An RC phase shift oscillator typically uses three RC stages to achieve the required 180° phase shift.
• Therefore, the correct answer is Three.

Answer: 3. 502 Hz

Explanation:

• The frequency of oscillation for an RC phase shift oscillator is given by:
  $f = \frac{1}{2\pi RC\sqrt{6}}$
  Substituting the values:
  $f = \frac{1}{2\pi \times 35 \times 3.7 \times 10^{-6} \times \sqrt{6}} \approx 502 \, Hz$
• Therefore, the correct answer is 502 Hz.

Answer: 2. Balancing the bridge

Explanation:

• In a Wein bridge oscillator, zero phase shift is achieved by balancing the bridge.
• Therefore, the correct answer is Balancing the bridge.

Answer: 3. 1

Explanation:

• For self-sustained oscillations, the condition $\beta A = 1$ must be satisfied, where $\beta$ is the feedback factor and $A$ is the gain.
• Therefore, the correct answer is 1.

Answer: 1. Phase-shift

Explanation:

• The given circuit is a phase-shift oscillator because it uses RC networks to achieve the required phase shift for oscillation.
• Therefore, the correct answer is Phase-shift.

Answer: 1. Hartley

Explanation:

• In a Hartley oscillator, the feedback signal is derived from an inductive voltage divider in the LC circuit.
• Therefore, the correct answer is Hartley.

Answer: 2. 29

Explanation:

• For a phase-shift oscillator, the gain of the amplifier stage must be greater than 29 to compensate for the attenuation in the RC network.
• Therefore, the correct answer is 29.

Answer: 3. Fundamental

Explanation:

• The minimum frequency at which a crystal will oscillate is its fundamental frequency.
• Therefore, the correct answer is Fundamental.

Answer: 2. Wien bridge

Explanation:

• The given circuit is a Wien bridge oscillator because it uses a Wien bridge network to achieve the required phase shift for oscillation.
• Therefore, the correct answer is Wien bridge.

Answer: 4. Connect integrator at the output

Explanation:

• A triangular wave generator can be derived from a square wave generator by connecting an integrator at the output.
• Therefore, the correct answer is Connect integrator at the output.

Answer: 2. Sawtooth waveform

Explanation:

• When an integrator produces waveforms with unequal rise and fall times, the output is called a sawtooth waveform.
• Therefore, the correct answer is Sawtooth waveform.

Answer: 3. Both $\beta A > 1$ and the phase shift around the feedback network must be 180°

Explanation:

• For oscillation, both the conditions $\beta A > 1$ and a 180° phase shift around the feedback network must be satisfied.
• Therefore, the correct answer is Both $\beta A > 1$ and the phase shift around the feedback network must be 180°.

Answer: 1. DC power into AC power

Explanation:

• An oscillator converts DC power into AC power to generate periodic waveforms.
• Therefore, the correct answer is DC power into AC power.

Answer: 3. Transistor

Explanation:

• In an LC transistor oscillator, the transistor is the active device that provides the necessary amplification for oscillation.
• Therefore, the correct answer is Transistor.

Answer: 1. Minimum

Explanation:

• In an LC circuit, when the capacitor energy is maximum, the inductor energy is minimum, and vice versa.
• Therefore, the correct answer is Minimum.

Answer: 4. Inversely proportional to square root of

Explanation:

• The frequency of an LC oscillator is given by:
  $f = \frac{1}{2\pi \sqrt{LC}}$
  Therefore, the frequency is inversely proportional to the square root of L or C.
• The correct answer is Inversely proportional to square root of.

Answer: 2. Undamped

Explanation:

• An oscillator produces undamped oscillations because it continuously supplies energy to maintain the oscillations.
• Therefore, the correct answer is Undamped.

Answer: 1. Positive

Explanation:

• An oscillator employs positive feedback to sustain oscillations.
• Therefore, the correct answer is Positive.

Answer: 1. Radio receivers

Explanation:

• The Hartley oscillator is commonly used in radio receivers due to its simplicity and stable frequency generation.
• Therefore, the correct answer is Radio receivers.

Answer: 2. Three

Explanation:

• A phase shift oscillator typically uses three RC sections to achieve the required 180° phase shift.
• Therefore, the correct answer is Three.