Semiconductor Devices PYQs Set 1 (PDF)

Set 1 of 17 · Questions 1-30 of 501

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Mere Teacher · Previous Year Questions JEE Main Physics · Semiconductor Devices · Set 1 (Q1-30)
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1. $In a CE amplifier, the input ac signal to be amplified is applied across$ (1) $forward biased emitter-base junction$ (2) $reverse biased collector-base junction$ (3) $reverse biased emitter-base junction$ (4) $forward biased collector-base junction.$ 2. $Match List I with List II List I (A) Rectifier (B) Stabilizer (C) Transformer (D) Filter List II (I) Used either for stepping up or stepping down the a.c. Voltage (II) Used to convert a.c. voltage into d.c. voltage (III) Used to remove any ripple in the rectified output voltage (IV) Used for constant output voltage even when the input voltage or load current change Chose the correct answer form the options given below:$ (1) $(A) - (II), (B) - (IV), (C) - (I), (D) - (III)$ (2) $(A) - (III), (B) - (IV), (C) - (I), (D) - (II)$ (3) $(A) - (II), (B) - (I), (C) - (IV), (D) - (II)$ (4) $(A) - (II), (B) - (I), (C) - (III), (D) - (IV)$ 3. $The input resistance of a silicon transistor is 100Ω . Base current is changed by 40 μA which results in a change in collector current by 2 mA . This transistor is used as a common‐emitter amplifier with a load resistance of4 kΩ . The voltage gain of the amplifier is [2012]$ (1) $2000$ (2) $3000$ (3) $4000$ (4) $1000$ 4. $Mobility of electrons in a semiconductor is defined as the ratio drift velocity to the applied electric field. If, for an n-type semiconductor, the density of electrons is 10^{19} m^{- 3} and their mobility is 1.6 m^{2} /(V.s) then the resistivity of the semiconductor (since it is an n-type semiconductor contribution of holes is ignored) is close to:$ (1) $2 Ωm$ (2) $4 Ωm$ (3) $0.4 Ωm$ (4) $0.2 Ωm$ 5. $The conductivity of semiconductor increases with increase in temperature because$ (1) $both number density of charge carriers and relaxation time increase$ (2) $number density of charge carriers increases$ (3) $number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density$ (4) $relaxation time increases.$ 6. $The input characteristics of a transistor in CE mode is the graph obtained by plotting$ (1) $I_{B} against V_{CE} at constant V_{BE}$ (2) $I_{B} against I_{C} at constant V_{BE}$ (3) $I_{B} against V_{BE} at constant V_{CE}$ (4) $I_{B} against I_{C} at constant V_{CE}$ 7. $The barrier potential of a p‐n junction depends on [2014] (i) Type of semiconductor material (ii) Amount of doping (iii) Temperature Which one of the following is correct?$ (1) $(i) and (ii) only$ (2) $(ii) only$ (3) $(ii) and (iii) only$ (4) $(i), (ii) and (iii)$ 8. $For a common emitter configuration, if α and β have their usual meanings, the incorrect relationship between α and β is.$ (1) $α = \frac{β}{1 - β}$ (2) $α = \frac{β}{1 + β}$ (3) $α = \frac{β ^{2}}{1 + β ^{2}}$ (4) $\frac{1}{α} = \frac{1}{β} + 1$ 9. $A working transistor with its three legs marked P, Q and R is tested using a mustimeter. No conduction is found between P and Q. By connecting the common (negative) terminal of the mustimeter to R and the other (positive) terminal to P or Q, some resistance is seen on the mustimeter. Which of following is true for the transistor?$ (1) $It is a pnp transistor with R as collector$ (2) $It is a pnp transistor with R as emitter$ (3) $It is an npn transistor with R as collector$ (4) $It is an npn transistor with R as base$ 10. $An LED is constructed from a p - n junction diode using GaAsP. The energy gap is 1.9 eV. The wavelength of the light emitted will be equal to [NEET 2019]$ (1) $10.4 \times 10^{- 26} m$ (2) $654 nm$ (3) $654Å$ (4) $654 \times 10^{- 11} m$ 11. $If A = 1 and B = 0, then in terms of Boolean algebra, A + B is equal to$ (1) $0$ (2) $B$ (3) $none of the above$ (4) $A$ 12. $For a p-type semiconductor, which of the following statements is true?$ (1) $Electrons are the majority carriers and pentavalent atoms are the dopants.$ (2) $Electrons are the majority carriers and trivalent atoms are the dopants.$ (3) $Holes are the majority carriers and trivalent atoms are the dopants.$ (4) $Holes are the majority carriers and pentavalent atoms are the dopants.$ 13. $By increasing the temperature, the specific resistance of a conductor and semiconductor:$ (1) $increases for both$ (2) $decreases for both$ (3) $increases, decreases respectively$ (4) $decreases, increases respectively$ 14. $Which logic gate produces 'LOW' output when any of the inputs is 'HIGH'?$ (1) $AND$ (2) $OR$ (3) $NAND$ (4) $NOR$ 15. $For a common emitter configuration, if ' α' and ' β' have their usual meanings, the incorrect relation between ' α' and ' β'$ (1) $\frac{1}{α} = \frac{1}{β} + 1$ (2) $α = \frac{β}{1 - β}$ (3) $α = \frac{β}{1 + β}$ (4) $\frac{1}{β} = \frac{1}{α} - 1$ 16. $The voltage gain of an amplifier with 9% negative feedback is 10. The voltage gain without feedback will be [2008]$ (1) $90$ (2) $10$ (3) $1.25$ (4) $100$ 17. $In a junction transistor, the collector current changes by 6.8 mA, if the emitter current is changed by 7 mA . For such transistor, the current amplification factor is$ (1) $30$ (2) $34$ (3) $40$ (4) $45$ 18. $A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of :$ (1) $each of these decreases$ (2) $copper strip increases and that of germanium decreases$ (3) $copper strip decreases and that of germanium increases$ (4) $each of these increases$ 19. $Pick out the statement which is not correct.$ (1) $At a low temperature, the resistance of a semiconductor is very high.$ (2) $Movement of holes is restricted to the valence band only.$ (3) $Width of the depletion region increases as the forward bias voltage increases in case of a N-P junction diode.$ (4) $In a forward bias condition, the diode heavily conducts.$ 20. $The intrinsic semiconductor becomes an insulator at$ (1) $0^{o} C$ (2) $- 10 0^{o} C$ (3) $30 0 K$ (4) $0 K$ 21. $In an oscillator, for sustained oscillations, Barkhausen criterion is Aβ equal to (A = voltage gain without feedback, β = feedback factor)$ (1) $zero$ (2) $1/2$ (3) $1$ (4) $2$ 22. $An LED is constructed from a pn junction based on a certain semi-conducting material whose energy gap is 1.9 eV . Then the wavelength of the emitted light is$ (1) $1.6 \times 10^{- 8} m$ (2) $9.1 \times 10^{- 5} m$ (3) $2.9 \times 10^{- 9} m$ (4) $6.5 \times 10^{- 7} m$ 23. $Consider a situation in which reverse biased current of a particular P-N junction increases when it is exposed to a light of wavelength \leq 621 nm . During this process, enhancement in carrier concentration takes place due to generation of hole-electron pairs. The value of band gap is nearly.$ (1) $2eV$ (2) $4eV$ (3) $1eV$ (4) $0.5eV$ 24. $If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be [2003]$ (1) $50 Hz$ (2) $70.7 Hz$ (3) $100 Hz$ (4) $25 Hz$ 25. $In forward biasing of the p-n junction :$ (1) $the positive terminal of the battery is connected to p-side and the depletion region becomes thick$ (2) $the positive terminal of the battery is connected to n-side and the depletion region becomes thin$ (3) $the positive terminal of the battery is connected to n-side and the depletion region becomes thick$ (4) $the positive terminal of the battery is connected to p-side and the depletion region becomes thin$ 26. $Barrier potential of a p‐n junction diode does not depend on [2003]$ (1) $Temperature$ (2) $Forward bias$ (3) $Doping density$ (4) $Diode design$ 27. $The peak voltage in the output of a half‐wave diode rectifier fed with a sinusoidal signal without filter is 10 V. The DC component of the output voltage is [2004]$ (1) $10/ 2 V$ (2) $10/ πV$ (3) $10 V$ (4) $20/ πV$ 28. $If the output of a NAND gate is given as input to a NOT gate, the resultant gate is$ (1) $AND$ (2) $OR$ (3) $NOR$ (4) $NOT$ 29. $The value of current gain α of a transistor is 0.98. The value of β will be [2002]$ (1) $4.9$ (2) $490$ (3) $59$ (4) $49$ 30. $A transistor is connected in common emitter circuit configuration, the collector supply voltage is 10V and the voltage drop across a resistor of 1000Ω in the collector circuit is 0.6V. If the current gain factor (β) is 24, then the base current is ___μA . (Round off to the Nearest Integer)$