Semiconductor Devices PYQs Set 5 (PDF)

Set 5 of 16 · Questions 121-150 of 467

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Mere Teacher · Previous Year Questions NEET Physics · Semiconductor Devices · Set 5 (Q121-150)
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121. $A common emitter amplifier has a voltage gain of 50, an input impedance of 100Ω and an output impedance of 200Ω . The power gain of the amplifier is [2007]$ (1) $500$ (2) $1000$ (3) $1250$ (4) $100$ 122. $The minimum potential difference between the base and emitter required to switch a silicon transistor ‘ON’ is approximately: [2006]$ (1) $3 V$ (2) $1 V$ (3) $5 V$ (4) $4.2 V$ 123. $Consider the following statements: (A) The junction area of solar cell is made very narrow compared to a photo diode. (B) Solar cells are not connected with any external bias. (C) LED is made of lightly doped p-n junction. (D) Increase of forward current results in continuous increase of LED light intensity. (E) LEDs have to be connected in forward bias for emission of light. Choose the correct answer from the options given below:$ (1) $B, E Only$ (2) $B, D, E Only$ (3) $A, C Only$ (4) $A, C, E Only$ 124. $Statement-I: By doping silicon semiconductor with pentavalent material, the electrons density increases. Statement-II: The n-type semiconductor has net negative charge. In the light of the above statements, choose the most appropriate answer from the options given below:$ (1) $Statement-I is true but Statement-II is false.$ (2) $Statement-I is false but Statement-II is true.$ (3) $Both Statement-I and Statement-II are true.$ (4) $Both Statement-I and Statement-II are false.$ 125. $Of the diodes shown in the following diagrams, which one is reverse biased? [2004]$ (1) (2) (3) (4) 126. $In a P-N junction diode which is not connected to any circuit-$ (1) $Potential is the same every where$ (2) $The P-type side is at a higher potential than the N-type side$ (3) $There is an electric field at the junction directed from the N-type side to the P-type side$ (4) $There is an electric field at the junction directed from the P-type side to the N-type side$ 127. $Which of the following gate is reversible:$ (1) (2) (3) (4) 128. $An npn transistor operates as a common emitter amplifier with a power gain of 60 dB. The input circuit resistance is 100Ω and the output load resistance is 10 kΩ. The common emitter current gain β is:$ (1) $10^{2}$ (2) $60$ (3) $6\times10²$ (4) $10^{4} .$ 129. $The effect of increase in temperature on the number of electrons in conduction band (n_{e}) and resistance of a semiconductor will be as:$ (1) $Both n_{e} and resistance decrease$ (2) $Both n_{e} and resistance increase$ (3) $n_{e} increases, resistance decreases$ (4) $n_{e} decreases, resistance increases$ 130. $A transistor is operated in common‐emitter configuration at V_{c} = 2 volt such that a change in the base current from 100 μA to 200 μA produces a change in the collector current from 5 mA to 10 mA . The current gain is [2009]$ (1) $75$ (2) $100$ (3) $150$ (4) $50$ 131. $In a transistor, the base current is 10 μA and the emitter current is 1 mA, then the collector current is$ (1) $990 μA$ (2) $100 μA$ (3) $1010 μA$ (4) $90 μA$ 132. $A p-n junction is fabricated from a semiconductor with band gap of 2.8 eV . What approximate wavelength it cannot detect?[use h = 6 \times 10^{- 34} m^{2} kg / s]$ (1) $100 nm$ (2) $200 nm$ (3) $400 nm$ (4) $600 nm$ 133. $A transistor is used as a common emitter amplifier with a load resistance 2 kΩ . The input resistance is 150Ω . Base current is changed by 20 μA which results in a change in collector current by 1.5 mA . The voltage gain of the amplifier is$ (1) $900$ (2) $1000$ (3) $1100$ (4) $1200$ 134. $The forbidden energy gap in Ge in 0.72 eV . Given, hc = 12400 eV - Å . The maximum wavelength of radiation that will generate electron hole pair is$ (1) $172220Å$ (2) $172.2Å$ (3) $17222Å$ (4) $1722Å$ 135. $In a transistor, when the emitter current changes by 9.85 mA, the collector current changes to 9.5 mA . Then the base current is$ (1) $0.05 mA$ (2) $0.85 mA$ (3) $0.8 mA$ (4) $0.35 mA$ 136. $Which of the following semi-conducting devices is used as voltage regulator?$ (1) $Zener diode$ (2) $LASER diode$ (3) $Photo diode$ (4) $Solar cell$ 137. $Mobility of electrons in semiconductor is defined as the ratio of their drift velocity to the applied electric field. If, for an n -type semiconductor, the density of electrons is 10^{19} m^{- 3} and their mobility is 1.6 m^{2} / (V . s) then the resistivity of the semiconductor (since it is an n-type semiconductor (since it is an n -type semiconductor contribution of holes is ignored) is close to :$ (1) $4Ω m$ (2) $0.4Ω m$ (3) $0.2Ω m$ (4) $2Ω m$ 138. $In an n-p-n common emitter (CE) transistor the collector current changes from 5 mA to 16 mA for the change in base current from 100 μ A and 200 μ A, respectively. The current gain of transistor is_____.$ (1) $110$ (2) $210$ (3) $0.9$ (4) $9$ 139. $Consider a n-type semiconductor in which ne and n_{h} are number of electrons and holes, respectively. (A) Holes are minority carriers(B) The dopant is a pentavalent atom(C) n_{e} n_{h} \neq = n_{i}^{2} (where n_{i} is number of electrons or holes in semiconductor when it is intrinsic form)(D) n_{e} n_{h} ⩾ n_{i}^{2} (E) The holes are not generated due to the donors Choose the correct answer from the options given below:$ (1) $(A), (B), (E) only$ (2) $(A), (C), (E) only$ (3) $(A), (B), (C) only$ (4) $(A), (C), (D) only$ 140. $The photo current in a photo diode depends on$ (1) $applied electric field$ (2) $frequency of the incident light$ (3) $wave length of incident light$ (4) $intensity of incident light$ 141. $In a CE transistor when the base current increases by 60 μA, change in base-emitter voltage is 1.2 V . Then the input resistance is$ (1) $1000Ω$ (2) $5000Ω$ (3) $2000Ω$ (4) $20000Ω$ 142. $To a germanium crystal equal number of aluminums and indium atoms are added. Then$ (1) $it remains an intrinsic semiconductor$ (2) $it becomes a n -type semiconductor$ (3) $it becomes a p-type semiconductor$ (4) $it becomes an insulator.$ 143. $Which one of the following bonds produces a solid that reflects light in the visible region and whose electrical conductivity decreases with temperature and has high melting point? [2010]$ (1) $metallic bonding$ (2) $van der Waals’ bonding$ (3) $ionic bonding$ (4) $covalent bonding$ 144. $The change in current through a junction diode is 1.2 mA when the forward bias voltage is changed by 0.6 V . The dynamic resistance is$ (1) $500Ω$ (2) $300Ω$ (3) $150Ω$ (4) $250Ω$ 145. $The photodiode is used to detect the optical signals. These diodes are preferably operated in reverse biased mode because.$ (1) $fractional change in majority carriers produce higher forward bias current$ (2) $fractional change in majority carriers produce higher reverse bias current$ (3) $fractional change in minority carriers produce higher forward bias current$ (4) $fractional change in minority carriers produce higher reverse bias current$ 146. $In a semi‐conducting material the mobilities of electrons and holes are μ_{e} and μ_{h} respectively, which of the following is true? [2005]$ (1) $μ_{e} < μ_{h}$ (2) $μ_{e} > μ_{h}$ (3) $μ_{e} = μ_{h}$ (4) $μ_{e} < 0; μ_{h} > 0$ 147. $The de common emitter current gain of a n-p-it transistor is 50 . The potential difference applicd across the collector and emitter of a transistor used in CF configuration is V_{CE} = 2 V . If the collector resistance R_{C} = 4 kΩ, the base current (I_{β}) and the collector current (I_{C}) are$ (1) $I_{B} = 10 μA, I_{C} = 0.5 mA$ (2) $I_{B} = 0.5 μA, I_{C} = 10 mA$ (3) $I_{B} = 5 μA, I_{C} = 1 mA$ (4) $I_{B} = 1 μA, I_{C} = 0.5 mA$ 148. $In a forward bias arrangement of a p - n junction diode, the$ (1) $direction of conventional current is from n -region to p -region in the diode$ (2) $p-region is connected negative terminal of the battery$ (3) $n -region is connected to the positive terminal of battery$ (4) $p-region is connected to the positive terminal of battery.$ 149. $Which of the following gate is called universal gate? [NEET 2020]$ (1) $OR gate$ (2) $AND gate$ (3) $NAND gate$ (4) $NOT gate$ 150. $When npn transistor is used as an amplifier$ (1) $electrons move from base to collector$ (2) $holes move from emitter to base$ (3) $electrons move from collector to base$ (4) $holes move from base to emitter$