{"id":978,"date":"2025-12-15T02:28:48","date_gmt":"2025-12-15T02:28:48","guid":{"rendered":"https:\/\/vracademy.in\/?p=978"},"modified":"2025-12-16T01:47:04","modified_gmt":"2025-12-16T01:47:04","slug":"semiconductor-devices-and-circuits","status":"publish","type":"post","link":"https:\/\/vracademy.in\/?p=978","title":{"rendered":"Semiconductor Devices and Circuits"},"content":{"rendered":"\n

Semiconductor Devices and Circuits<\/h2>\n\n\n\n
\"\"<\/figure>\n\n\n\n

Semiconductor Devices and Circuits:<\/h1>\n\n\n\n

100 Multiple Choice Questions<\/h2>\n\n\n\n

Section A: Diodes and Physics<\/h3>\n\n\n\n
    \n
  1. In a PN junction, the depletion region contains: A) Free electrons B) Free holes C) Immobile ions D) Neutral atoms<\/li>\n\n\n\n
  2. The width of the depletion layer of a PN junction diode ________ with increase in reverse bias. A) Decreases B) Increases C) Remains constant D) Becomes zero<\/li>\n\n\n\n
  3. The potential barrier of a Silicon diode at room temperature is approximately: A) 0.3 V B) 0.7 V C) 1.1 V D) 1.5 V<\/li>\n\n\n\n
  4. Zener breakdown occurs primarily due to: A) Impact ionization B) High doping concentration and strong electric field C) Thermal heating D) High reverse current<\/li>\n\n\n\n
  5. Avalanche breakdown is observed in: A) Lightly doped diodes B) Heavily doped diodes C) Forward biased diodes D) Zener diodes below 5V<\/li>\n\n\n\n
  6. A varactor diode acts as a variable: A) Resistor B) Inductor C) Capacitor D) Source<\/li>\n\n\n\n
  7. The main application of a Tunnel diode is in: A) Rectification B) High-speed switching and oscillators C) Audio amplification D) Voltage regulation<\/li>\n\n\n\n
  8. Which diode shows a negative resistance region in its V-I characteristics? A) Zener Diode B) LED C) Tunnel Diode D) Schottky Diode<\/li>\n\n\n\n
  9. In a solar cell, the open-circuit voltage is typically around: A) 0.1 V B) 0.5 to 0.6 V C) 2.0 V D) 12 V<\/li>\n\n\n\n
  10. The capacitance appearing across a reverse-biased semiconductor junction is called: A) Storage capacitance B) Diffusion capacitance C) Transition capacitance D) Plate capacitance<\/li>\n\n\n\n
  11. Diffusion capacitance is dominant in: A) Reverse bias region B) Forward bias region C) Zero bias region D) Breakdown region<\/li>\n\n\n\n
  12. An ideal diode acts as a ________ when forward biased and as a ________ when reverse biased. A) Open switch, Closed switch B) Closed switch, Open switch C) Resistor, Inductor D) Source, Sink<\/li>\n\n\n\n
  13. The dynamic resistance of a diode is proportional to: A) Current B) 1 \/ Current C) Current squared D) Voltage<\/li>\n\n\n\n
  14. For a Zener diode to work as a voltage regulator, it must be connected in: A) Forward bias B) Reverse bias C) Series with load D) Parallel with source<\/li>\n\n\n\n
  15. Schottky diodes are known for: A) High noise B) Slow switching C) Low forward voltage drop and fast switching D) High reverse breakdown voltage<\/li>\n<\/ol>\n\n\n\n

    Section B: Rectifiers and Filters<\/h3>\n\n\n\n
      \n
    1. The maximum efficiency of a half-wave rectifier is: A) 40.6% B) 50% C) 81.2% D) 100%<\/li>\n\n\n\n
    2. The ripple factor of a full-wave rectifier is: A) 1.21 B) 0.48 C) 0.1 D) 2.0<\/li>\n\n\n\n
    3. In a bridge rectifier, the Peak Inverse Voltage (PIV) across each non-conducting diode is: A) $V_m$ B) $2V_m$ C) $V_m \/ 2$ D) $4V_m$<\/li>\n\n\n\n
    4. Which rectifier requires a center-tapped transformer? A) Half-wave B) Bridge C) Full-wave (two diode) D) None<\/li>\n\n\n\n
    5. A capacitor filter connected across a rectifier output: A) Increases ripple B) Decreases DC output voltage C) Increases DC output voltage and reduces ripple D) Has no effect<\/li>\n\n\n\n
    6. If the line frequency is 50 Hz, the ripple frequency in a full-wave rectifier is: A) 50 Hz B) 100 Hz C) 25 Hz D) 200 Hz<\/li>\n\n\n\n
    7. The DC output voltage of a bridge rectifier with peak input $V_m$ is: A) $V_m \/ \\pi$ B) $2V_m \/ \\pi$ C) $V_m \/ 2$ D) $V_m$<\/li>\n\n\n\n
    8. Which filter is most suitable for heavy loads (large currents)? A) Capacitor filter B) Inductor (Choke) filter C) RC filter D) None of these<\/li>\n\n\n\n
    9. A voltage doubler circuit uses: A) Diodes and Resistors B) Diodes and Inductors C) Diodes and Capacitors D) Transistors<\/li>\n\n\n\n
    10. Regulation is defined as the change in output voltage from: A) Zero load to Full load B) 10% load to 50% load C) Input to Output D) Low temp to High temp<\/li>\n<\/ol>\n\n\n\n

      Section C: Transistors (BJT)<\/h3>\n\n\n\n
        \n
      1. In a BJT, the most heavily doped region is: A) Base B) Collector C) Emitter D) All are equal<\/li>\n\n\n\n
      2. The base of a transistor is made very thin to: A) Reduce cost B) Allow heat dissipation C) Reduce recombination of charge carriers D) Increase voltage rating<\/li>\n\n\n\n
      3. The relation between $\\alpha$ and $\\beta$ is: A) $\\beta = \\alpha \/ (1 – \\alpha)$ B) $\\beta = \\alpha \/ (1 + \\alpha)$ C) $\\alpha = \\beta \/ (1 – \\beta)$ D) $\\beta = 1 – \\alpha$<\/li>\n\n\n\n
      4. If $\\alpha = 0.98$, the value of $\\beta$ is: A) 49 B) 98 C) 100 D) 0.02<\/li>\n\n\n\n
      5. In the active region of a transistor: A) E-B junction is reverse biased, C-B is forward biased B) E-B is forward biased, C-B is reverse biased C) Both junctions are forward biased D) Both junctions are reverse biased<\/li>\n\n\n\n
      6. A transistor acts as a closed switch in the: A) Active region B) Cutoff region C) Saturation region D) Inverse active region<\/li>\n\n\n\n
      7. The input impedance of a Common Collector (CC) configuration is: A) Very low B) Zero C) Medium D) Very high<\/li>\n\n\n\n
      8. Which configuration produces a phase shift of $180^\\circ$ between input and output? A) Common Base B) Common Collector C) Common Emitter D) All of them<\/li>\n\n\n\n
      9. The leakage current $I_{CEO}$ is related to $I_{CBO}$ by: A) $I_{CEO} = I_{CBO}$ B) $I_{CEO} = (1+\\beta) I_{CBO}$ C) $I_{CEO} = \\beta I_{CBO}$ D) $I_{CEO} = I_{CBO} \/ (1+\\beta)$<\/li>\n\n\n\n
      10. Ideally, the stability factor $S$ should be: A) As high as possible B) As low as possible (close to 1) C) Equal to $\\beta$ D) Zero<\/li>\n\n\n\n
      11. Thermal runaway in a transistor occurs due to increase in: A) Base current B) Collector reverse leakage current C) Emitter resistance D) Supply voltage<\/li>\n\n\n\n
      12. The voltage divider bias is also known as: A) Fixed bias B) Base resistor bias C) Self bias (Universal bias) D) Feedback bias<\/li>\n\n\n\n
      13. The Early Effect in a BJT refers to: A) Base width modulation by collector voltage B) Heating of the collector C) Breakdown of the emitter D) Increase in $\\beta$ with temperature<\/li>\n\n\n\n
      14. For amplification, the BJT is operated in: A) Saturation B) Cutoff C) Active region D) Breakdown<\/li>\n\n\n\n
      15. In a PNP transistor, the majority carriers in the emitter are: A) Electrons B) Holes C) Both equal D) Ions<\/li>\n\n\n\n
      16. A Common Base amplifier has a current gain ($\\alpha$) of: A) Much greater than 1 B) Equal to $\\beta$ C) Less than 1 D) Zero<\/li>\n\n\n\n
      17. Which amplifier configuration is used for impedance matching? A) Common Emitter B) Common Base C) Common Collector (Emitter Follower) D) Differential Amplifier<\/li>\n\n\n\n
      18. The Q-point in a transistor amplifier represents: A) The cutoff point B) The saturation point C) The DC operating point D) The AC maximum gain<\/li>\n\n\n\n
      19. The crossover distortion occurs in: A) Class A amplifiers B) Class B push-pull amplifiers C) Class C amplifiers D) Common Base amplifiers<\/li>\n\n\n\n
      20. The maximum theoretical efficiency of a Class B amplifier is: A) 25% B) 50% C) 78.5% D) 100%<\/li>\n\n\n\n
      21. Which transistor configuration has the highest power gain? A) CB B) CC C) CE D) All equal<\/li>\n\n\n\n
      22. In a fixed bias circuit, the operating point shifts due to changes in: A) Temperature and $\\beta$ B) Capacitor values C) Input frequency D) Load resistance<\/li>\n\n\n\n
      23. The bypass capacitor in a CE amplifier is used to: A) Block DC B) Bypass the emitter resistor to prevent AC gain reduction C) Couple stages D) Filter noise<\/li>\n\n\n\n
      24. An emitter follower has a voltage gain of: A) > 100 B) Equal to $\\beta$ C) Approximately 1 (slightly less) D) Infinite<\/li>\n\n\n\n
      25. The output characteristics of a CE transistor is a plot between: A) $I_B$ and $V_{BE}$ B) $I_C$ and $V_{CE}$ C) $I_E$ and $V_{CB}$ D) $I_C$ and $I_B$<\/li>\n<\/ol>\n\n\n\n

        Section D: Field Effect Transistors (FET)<\/h3>\n\n\n\n
          \n
        1. A JFET is a ________ controlled device. A) Current B) Voltage C) Power D) Resistance<\/li>\n\n\n\n
        2. The input impedance of a JFET is: A) Very low B) Very high ($> 1 M\\Omega$) C) Zero D) Same as BJT<\/li>\n\n\n\n
        3. The gate-source junction of a JFET is always: A) Forward biased B) Reverse biased C) Unbiased D) Grounded<\/li>\n\n\n\n
        4. The Pinch-off voltage ($V_P$) in a JFET is the voltage at which: A) Drain current becomes zero B) Drain current saturates C) Gate current becomes maximum D) Breakdown occurs<\/li>\n\n\n\n
        5. In an N-channel JFET, the carriers are: A) Holes B) Electrons C) Ions D) Both A and B<\/li>\n\n\n\n
        6. MOSFET stands for: A) Metal Oxide Silicon Field Effect Transistor B) Metal Oxide Semiconductor Field Effect Transistor C) Metal Organic Semiconductor Field Effect Transistor D) Metallic Oxide Source FET<\/li>\n\n\n\n
        7. The insulating layer in a MOSFET is usually made of: A) Silicon B) Silicon Dioxide ($SiO_2$) C) Germanium D) Copper<\/li>\n\n\n\n
        8. Which MOSFET can operate in both depletion and enhancement modes? A) D-MOSFET B) E-MOSFET C) JFET D) UJT<\/li>\n\n\n\n
        9. The transconductance ($g_m$) of a FET is defined as: A) $\\Delta I_D \/ \\Delta V_{GS}$ B) $\\Delta V_{GS} \/ \\Delta I_D$ C) $\\Delta I_D \/ \\Delta V_{DS}$ D) $\\Delta V_{DS} \/ \\Delta I_D$<\/li>\n\n\n\n
        10. E-MOSFETs are normally ________ devices. A) ON B) OFF C) Shorted D) Conducting<\/li>\n\n\n\n
        11. CMOS technology uses: A) Only NMOS B) Only PMOS C) Both NMOS and PMOS D) BJTs and FETs<\/li>\n\n\n\n
        12. The channel in a JFET is controlled by: A) Depletion region width B) Oxide thickness C) Doping level only D) Thermal agitation<\/li>\n\n\n\n
        13. At pinch-off, the channel width is: A) Maximum B) Minimum (effectively closed) C) Zero D) Unchanged<\/li>\n\n\n\n
        14. FETs have ________ thermal stability compared to BJTs. A) Better B) Worse C) Equal D) No<\/li>\n\n\n\n
        15. The relation between drain current and gate voltage in a JFET is: A) Linear B) Quadratic (Square law) C) Exponential D) Logarithmic<\/li>\n<\/ol>\n\n\n\n

          Section E: Amplifiers<\/h3>\n\n\n\n
            \n
          1. An RC coupled amplifier is widely used for: A) DC amplification B) Voltage amplification in audio range C) RF amplification D) Power amplification<\/li>\n\n\n\n
          2. The fall in gain at low frequencies in an RC coupled amplifier is due to: A) Transistor beta B) Coupling and Bypass capacitors C) Shunt capacitance D) Wiring inductance<\/li>\n\n\n\n
          3. The fall in gain at high frequencies is due to: A) Coupling capacitors B) Inter-electrode and stray shunt capacitances C) Resistors D) Power supply<\/li>\n\n\n\n
          4. The bandwidth of an amplifier is the range of frequencies where gain is at least: A) 50% of max B) 70.7% ($-3$ dB) of max C) 90% of max D) 100% of max<\/li>\n\n\n\n
          5. Class A amplifier conduction angle is: A) $90^\\circ$ B) $180^\\circ$ C) $270^\\circ$ D) $360^\\circ$<\/li>\n\n\n\n
          6. Transformer coupling is used primarily for: A) Impedance matching and power transfer B) Voltage gain C) Reducing cost D) High frequency response<\/li>\n\n\n\n
          7. In a multistage amplifier, the total gain in dB is the ________ of individual gains in dB. A) Product B) Sum C) Difference D) Ratio<\/li>\n\n\n\n
          8. The Miller Effect results in an increase in: A) Input capacitance B) Output resistance C) Voltage gain D) Bandwidth<\/li>\n\n\n\n
          9. A Darlington pair connects two transistors to achieve: A) Very high voltage gain B) Very high current gain and input impedance C) Low input impedance D) High frequency operation<\/li>\n\n\n\n
          10. Distortion caused by non-linear characteristics of the device is called: A) Frequency distortion B) Phase distortion C) Harmonic (Amplitude) distortion D) Noise<\/li>\n\n\n\n
          11. If the gain is 100 and bandwidth is 10 kHz, the Gain-Bandwidth Product (GBW) is: A) $10^5$ Hz B) $10^6$ Hz C) $10^4$ Hz D) 100 Hz<\/li>\n\n\n\n
          12. Class C amplifiers are used in: A) Audio amplifiers B) RF Tuned amplifiers C) Oscillators D) Linear power supplies<\/li>\n\n\n\n
          13. The efficiency of a Class A amplifier with resistive load is maximum: A) 25% B) 50% C) 78.5% D) 90%<\/li>\n\n\n\n
          14. Noise in an amplifier is least in: A) Carbon resistors B) Wire wound resistors C) FETs D) Metal film resistors<\/li>\n\n\n\n
          15. A differential amplifier amplifies: A) The sum of input signals B) The difference of input signals C) Only one signal D) Common mode signals<\/li>\n<\/ol>\n\n\n\n

            Section F: Feedback and Oscillators<\/h3>\n\n\n\n
              \n
            1. Negative feedback in an amplifier: A) Increases gain B) Reduces bandwidth C) Increases stability and bandwidth D) Increases distortion<\/li>\n\n\n\n
            2. The gain of an amplifier with feedback ($A_f$) is given by: A) $A \/ (1 – A\\beta)$ B) $A \/ (1 + A\\beta)$ C) $A(1 + A\\beta)$ D) $1 \/ \\beta$<\/li>\n\n\n\n
            3. The product $A\\beta$ is called: A) Closed loop gain B) Open loop gain C) Loop gain D) Feedback factor<\/li>\n\n\n\n
            4. Emitter follower uses ________ feedback. A) Voltage Series Negative B) Current Series Negative C) Voltage Shunt Negative D) Positive<\/li>\n\n\n\n
            5. Positive feedback is necessary for: A) Stabilization B) Oscillation C) Noise reduction D) Bandwidth extension<\/li>\n\n\n\n
            6. The Barkhausen criterion for oscillation is: A) $|A\\beta| = 1$ and phase shift $0^\\circ$ or $360^\\circ$ B) $|A\\beta| < 1$ C) Phase shift $180^\\circ$ D) $|A\\beta| = 0$<\/li>\n\n\n\n
            7. Which oscillator uses a split capacitor tank circuit? A) Hartley B) Colpitts C) RC Phase Shift D) Wien Bridge<\/li>\n\n\n\n
            8. A Hartley oscillator uses: A) Tapped inductor B) Tapped capacitor C) RC network D) Crystal<\/li>\n\n\n\n
            9. An RC Phase Shift oscillator generally uses: A) 1 RC section B) 2 RC sections C) 3 RC sections D) 4 RC sections<\/li>\n\n\n\n
            10. The most stable oscillator for frequency is: A) Hartley B) Colpitts C) Crystal Oscillator D) Wien Bridge<\/li>\n\n\n\n
            11. In a Wien Bridge oscillator, the feedback network provides zero phase shift at frequency: A) $1 \/ (2\\pi RC)$ B) $1 \/ (2\\pi\\sqrt{LC})$ C) $1 \/ (4\\pi RC)$ D) $RC$<\/li>\n\n\n\n
            12. Negative feedback ________ input impedance in voltage-series feedback. A) Decreases B) Increases C) Keeps constant D) Makes zero<\/li>\n\n\n\n
            13. A multivibrator is a type of: A) Sinusoidal oscillator B) Relaxation oscillator (Square wave generator) C) Amplifier D) Rectifier<\/li>\n\n\n\n
            14. The feedback fraction $\\beta$ is: A) Output \/ Input B) Feedback Voltage \/ Output Voltage C) Input \/ Output D) Gain \/ Input<\/li>\n\n\n\n
            15. If $A = 100$ and $\\beta = 0.09$, the gain with negative feedback is approx: A) 90 B) 100 C) 10 D) 9<\/li>\n\n\n\n
            16. Crystal oscillators work on the principle of: A) Photoelectric effect B) Piezoelectric effect C) Compton effect D) Hall effect<\/li>\n\n\n\n
            17. Current-shunt negative feedback behaves as a: A) Voltage amplifier B) Current amplifier C) Transresistance amplifier D) Transconductance amplifier<\/li>\n\n\n\n
            18. To start oscillations, initially $|A\\beta|$ must be: A) Exactly 1 B) Slightly greater than 1 C) Less than 1 D) Zero<\/li>\n\n\n\n
            19. An astable multivibrator has: A) One stable state B) Two stable states C) No stable states D) Three stable states<\/li>\n\n\n\n
            20. The active element in a Phase Shift oscillator is typically: A) Diode B) Transformer C) Transistor or Op-Amp D) Inductor<\/li>\n<\/ol>\n\n\n\n

              Part 3: Answer Key and Detailed Solutions<\/h2>\n\n\n\n

              1. C)<\/strong> The depletion region is formed by the recombination of electrons and holes, leaving behind immobile positive and negative ions. 2. B)<\/strong> Reverse bias pulls carriers away from the junction, widening the depletion layer. 3. B)<\/strong> For Silicon, the barrier potential is $\\approx 0.7V$; for Germanium, it is $\\approx 0.3V$. 4. B)<\/strong> Zener breakdown happens in heavily doped diodes where the narrow depletion region creates a strong electric field, pulling electrons from bonds. 5. A)<\/strong> Avalanche breakdown occurs in lightly doped diodes due to carrier collision\/impact ionization at high voltages. 6. C)<\/strong> A reverse-biased diode acts as a capacitor where the depletion width (dielectric) varies with voltage. 7. B)<\/strong> Tunnel diodes exhibit negative resistance, making them useful for high-speed switching and microwave oscillators. 8. C)<\/strong> Due to quantum tunneling, current decreases as voltage increases in a specific range. 9. B)<\/strong> A single silicon solar cell typically produces about 0.5V to 0.6V DC. 10. C)<\/strong> Transition (or depletion) capacitance dominates in reverse bias due to charge separation by the depletion layer. 11. B)<\/strong> Diffusion capacitance dominates in forward bias due to the storage of minority carriers near the junction. 12. B)<\/strong> Ideally, it’s a perfect conductor (switch closed) in forward bias and a perfect insulator (switch open) in reverse bias. 13. B)<\/strong> Dynamic resistance $r_d = \\eta V_T \/ I$. It is inversely proportional to the DC bias current $I$. 14. B)<\/strong> Zener diodes are designed to work in the reverse breakdown region to maintain constant voltage. 15. C)<\/strong> Schottky diodes use a metal-semiconductor junction, resulting in no minority carrier storage, low voltage drop, and fast switching. 16. A)<\/strong> The theoretical maximum efficiency is $40.6\\%$. 17. B)<\/strong> Full-wave rectifiers have a lower AC component (ripple) with $\\gamma = 0.48$. 18. A)<\/strong> In a bridge, two diodes conduct at a time, so the reverse voltage across the OFF diodes is shared, effectively $V_m$ (unlike $2V_m$ in center-tapped). 19. C)<\/strong> A standard full-wave rectifier uses a center-tapped transformer; a bridge does not. 20. C)<\/strong> A capacitor charges to the peak voltage and discharges slowly, raising the average DC and smoothing the waveform (reducing ripple). 21. B)<\/strong> For full-wave, the output pulses twice per input cycle. $2 \\times 50 = 100$ Hz. 22. B)<\/strong> $V_{dc} = 2V_m \/ \\pi \\approx 0.636 V_m$. 23. B)<\/strong> An inductor opposes current change. At heavy loads (high current), it filters effectively. Capacitor filters drop voltage at heavy loads. 24. C)<\/strong> Voltage doublers use a network of diodes and capacitors to clamp and stack voltages. 25. A)<\/strong> Regulation $\\% = (V_{no-load} – V_{full-load}) \/ V_{full-load} \\times 100$. 26. C)<\/strong> The Emitter is heavily doped to inject a large number of carriers into the base. 27. C)<\/strong> A thin base ensures that most carriers injected from the emitter pass through to the collector without recombining in the base. 28. A)<\/strong> $\\beta = I_C\/I_B$ and $\\alpha = I_C\/I_E$. Algebra yields $\\beta = \\alpha \/ (1-\\alpha)$. 29. A)<\/strong> $\\beta = 0.98 \/ (1 – 0.98) = 0.98 \/ 0.02 = 49$. 30. B)<\/strong> Active region (Amplification): Emitter-Base forward biased, Collector-Base reverse biased. 31. C)<\/strong> Saturation region: Both junctions forward biased, acting like a short (closed switch). 32. D)<\/strong> CC (Emitter Follower) has high input impedance and low output impedance. 33. C)<\/strong> Common Emitter configuration inverts the signal ($180^\\circ$ shift). 34. B)<\/strong> $I_{CEO}$ is the leakage current from Collector to Emitter with Base open. It is amplified by the transistor: $(1+\\beta)I_{CBO}$. 35. B)<\/strong> Stability factor $S$ measures change in $I_C$. Lower $S$ (ideally 1) means better stability against temperature changes. 36. B)<\/strong> Leakage current increases with temperature, increasing $I_C$, which increases heat, leading to a cycle (runaway). 37. C)<\/strong> It makes the operating point independent of $\\beta$, hence “Universal”. 38. A)<\/strong> Higher $V_{CB}$ widens the collector depletion region, narrowing the effective base width (Base Width Modulation). 39. C)<\/strong> The active region provides linear amplification. 40. B)<\/strong> In PNP, P-type emitter injects Holes. 41. C)<\/strong> $I_C < I_E$, so $\\alpha < 1$. 42. C)<\/strong> CC (Emitter Follower) matches high Z source to low Z load. 43. C)<\/strong> Quiescent point: The DC voltage and current values when no signal is applied. 44. B)<\/strong> Occurs when the transistor is switching on\/off at the zero crossing (dead zone) in Push-Pull Class B. 45. C)<\/strong> $\\pi \/ 4 \\approx 78.5\\%$. 46. C)<\/strong> CE has both voltage and current gain, giving the highest Power Gain. 47. A)<\/strong> Fixed bias is very unstable with respect to temperature and $\\beta$ variations. 48. B)<\/strong> Without it, the emitter resistor provides negative feedback, reducing the AC gain. The capacitor shorts AC to ground. 49. C)<\/strong> Gain is slightly less than 1, but usually treated as unity. 50. B)<\/strong> Plot of $I_C$ vs $V_{CE}$ for constant $I_B$. 51. B)<\/strong> The Gate voltage controls the electric field which controls the current. 52. B)<\/strong> The gate is reverse biased, drawing almost zero current. 53. B)<\/strong> To maintain high input impedance and control depletion width. 54. B)<\/strong> $V_P$ is the voltage where the channel is fully depleted (pinched), and current saturates (becomes constant). 55. B)<\/strong> N-channel uses electrons (faster mobility than holes). 56. B)<\/strong> Metal Oxide Semiconductor Field Effect Transistor. 57. B)<\/strong> A silicon dioxide layer insulates the gate from the channel. 58. A)<\/strong> Depletion MOSFET (D-MOSFET) works with zero bias (channel exists) and can be depleted or enhanced. 59. A)<\/strong> Transconductance is the ratio of change in output current to change in input voltage. 60. B)<\/strong> E-MOSFETs have no physical channel at 0V. They need a gate voltage to turn ON. 61. C)<\/strong> Complementary MOS uses paired NMOS and PMOS for low power. 62. A)<\/strong> Reverse bias increases depletion width, narrowing the conductive channel. 63. B)<\/strong> It is not physically zero (current still flows), but it is minimum\/constricted. 64. A)<\/strong> FETs have a negative temperature coefficient (resistivity increases with temp), preventing thermal runaway. 65. B)<\/strong> Shockley\u2019s equation: $I_D = I_{DSS}(1 – V_{GS}\/V_P)^2$. 66. B)<\/strong> Voltage amplification for audio signals. 67. B)<\/strong> Capacitors have high reactance ($X_C = 1\/2\\pi fC$) at low frequencies, blocking the signal. 68. B)<\/strong> Shunt (parasitic) capacitances short the signal to ground at high frequencies. 69. B)<\/strong> $1\/\\sqrt{2}$ of voltage gain corresponds to -3dB power point. 70. D)<\/strong> Conducts for the full cycle ($360^\\circ$). 71. A)<\/strong> Transformers transform impedance ($n^2$) for max power transfer. 72. B)<\/strong> Gains in decibels are additive. $20dB + 10dB = 30dB$. 73. A)<\/strong> Miller effect multiplies the feedback capacitance by $(1+A)$, increasing input capacitance and reducing HF gain. 74. B)<\/strong> Cascading two transistors provides extremely high $\\beta$ ($\\beta_1 \\times \\beta_2$) and high input Z. 75. C)<\/strong> Introduction of frequencies (harmonics) not present in the input. 76. B)<\/strong> $100 \\times 10^4 = 10^6$ Hz. 77. B)<\/strong> Conducts for $< 180^\\circ$. High efficiency, used with tuned LC circuits in RF. 78. A)<\/strong> With a resistive load, max efficiency is 25%. With transformer load, 50%. 79. D)<\/strong> Metal film resistors have lower thermal noise than carbon. 80. B)<\/strong> It amplifies the difference ($V_1 – V_2$) and rejects common signals (noise). 81. C)<\/strong> Negative feedback trades gain for stability, linearity, and bandwidth. 82. B)<\/strong> The standard feedback formula. 83. C)<\/strong> Loop gain determines the stability margins. 84. A)<\/strong> Voltage is sampled (parallel\/shunt output) and mixed in series (opposing $V_{in}$ in loop). Correction: Emitter Follower is Voltage-Series feedback.<\/em> Output is Voltage (Emitter), Feedback is proportional to V_out, applied in Series with input. 85. B)<\/strong> Positive feedback (regeneration) sustains oscillations. 86. A)<\/strong> Loop gain magnitude must be 1, and phase shift around the loop must be $0^\\circ$ or $360^\\circ$ (positive feedback). 87. B)<\/strong> Colpitts uses a tapped capacitor divider. 88. A)<\/strong> Hartley uses a tapped inductor. 89. C)<\/strong> Each RC section provides up to $90^\\circ$ (practically $60^\\circ$). 3 sections provide $180^\\circ$ total shift. 90. C)<\/strong> Crystals have very high Q-factor, providing precise frequency stability. 91. A)<\/strong> Frequency of oscillation for Wien Bridge. 92. B)<\/strong> Series mixing increases input impedance ($Z_{in}(1+A\\beta)$). 93. B)<\/strong> It generates non-sinusoidal waves (square waves) by switching states. 94. B)<\/strong> $\\beta = V_f \/ V_{out}$. It represents the fraction of output fed back. 95. C)<\/strong> $A_f = 100 \/ (1 + 100\\times 0.09) = 100 \/ 10 = 10$. 96. B)<\/strong> Mechanical stress creates voltage and vice-versa. 97. B)<\/strong> Current sampling (increases $R_{out}$) and shunt mixing (decreases $R_{in}$) stabilizes current gain. 98. B)<\/strong> Slightly $>1$ to overcome losses and build up amplitude from noise. 99. C)<\/strong> Astable has no stable states; it continuously switches (oscillates). 100. C)<\/strong> The RC network provides phase shift, the active device (Transistor\/Op-Amp) provides gain to overcome attenuation.<\/p>\n","protected":false},"excerpt":{"rendered":"

              Semiconductor Devices and Circuits Semiconductor Devices and Circuits: 100 Multiple Choice Questions Section A: Diodes and Physics Section B: Rectifiers and Filters Section C: Transistors…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-978","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/posts\/978","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/vracademy.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=978"}],"version-history":[{"count":1,"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/posts\/978\/revisions"}],"predecessor-version":[{"id":980,"href":"https:\/\/vracademy.in\/index.php?rest_route=\/wp\/v2\/posts\/978\/revisions\/980"}],"wp:attachment":[{"href":"https:\/\/vracademy.in\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=978"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vracademy.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=978"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vracademy.in\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=978"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}