JEE Questions for Physics Semiconductor Devices Quiz 14 - MCQExams.com

The value of plate current in the given circuit diagram will be
Physics-Semiconductor Devices-87956.png
  • 3 mA
  • 8 mA
  • 13 mA
  • 18 mA
Coating of strontium oxide on tungsten cathode in a valve is good for thermionic emission because
  • Work function decreases
  • Work function increases
  • Conductivity of cathode increases
  • Cathode can be heated to high temperature
Plate resistance of two triode valves is 2 kΩ and 4 kΩ, amplification factor of each of the valves is 40. The ratio of voltage amplification, when used with 4 kΩ load resistance, will be
  • 10
  • 4/3
  • 3/4
  • 16/3
Diode is used as a/an
  • Oscillator
  • Amplifier
  • Rectifier
  • Modulator
The electrical circuits used to get smooth DC output from a rectifier circuit is called
  • Filter
  • Amplifier
  • Full wave rectifier
  • Oscillator
Which of the following does not vary with plate or grid voltages?
  • gm
  • RP
  • µ
  • Each of them varies
The grid in a triode valve is used
  • To increases the thermionic emission
  • To control the plate to cathode current
  • To reduce the inter-electrode capacity
  • To keep cathode at constant potential
In a triode valve the amplification factor is 20 and mutual conductance is 10–3 mho. The plate resistance is
  • 2 × 103 Ω
  • 4 × 103 Ω
  • 2 × 104 Ω
  • 2 × 105 Ω
The thermionic emission of electron is due to
  • Electromagnetic field
  • Electrostatic field
  • High temperature
  • Photoelectric effect
The slope of plate characteristic of a vacuum diode is 2 × 10–2 mA/V. The plate resistance of diode will be
  • 50Ω
  • 50 kΩ
  • 500Ω
  • 500 kΩ
The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature
  • Decreases exponentially with increasing band gap
  • Increases exponentially with increasing band gap
  • Decreases with increasing temperature
  • Is independent of the temperature and the band gap
The typical ionisation energy of a donor in silicon is
  • 10.0 eV
  • 1.0 eV
  • 0.1 eV
  • 0.001 eV
In PN-junction diode the reverse saturation current is 10–5 amp at 27° C. The forward current for a voltage of 0.2 volt is [exp (7.= 2038.6, k = 1.4 × 10–23J /K]
  • 2037.6 × 10–3 amp
  • 203.76 × 10–3 amp
  • 20.376 × 10–3 amp
  • 2.0376 × 103 amp
A 2 V battery is connected across the points A and B as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to A is
Physics-Semiconductor Devices-87965.png
  • 0.2 A
  • 0.4 A
  • Zero
  • 0.1 A
A P-type semiconductor has acceptor levels 57 meV above the valence band. The maximum wavelength of light required to create a hole is (Planck\'s constant h = 6.6 × 10–34J - s)
  • 57 Å
  • 57 × 10–3 Å
  • 217100 Å
  • 11.61 × 10–33 Å
The diode used in the circuit shown in the figure has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milliwatts. What should be the value of the resistor R, connected in series with the diode for obtaining maximum current?
Physics-Semiconductor Devices-87968.png
  • 1.5 Ω
  • 5 Ω
  • 6.67 Ω
  • 200 Ω
For a transistor amplifier in common emitter configuration for load impedance of 1 kΩ (hfe = 50 and hoe = 25µA /V) the current gain is
  • –5.2
  • –15.7
  • –24.8
  • –48.78
In semiconductor the concentrations of electrons and holes are 8 × 1018 /m3 and 5 × 1018 /m respectively. If the mobilities of electrons and holes are 2.3m2 /volt - s and 0.01 m2 /volt - s respectively, then semiconductor is
  • N-type and its resistivity is 0.34 ohm-metre
  • P-type and its resistivity is 0.034 ohm-metre
  • N-type and its resistivity is 0.034 ohm-metre
  • P-type and its resistivity is 3.40 ohm-metre
For a cubic crystal structure which one of the following relations indicating the cell characteristics in correct?
  • a ≠ b ≠ c and α ≠ β ≠ γ ≠ 90°
  • a ≠ b ≠ c and α = β = γ = 90°
  • a = b = c and α ≠ β ≠ γ ≠ 90°
  • a = b = c and α = β = γ = 90°
A sinusoidal voltage of peak value 200 volt is connected to a diode and resistor R in the circuit shown so that half wave rectification occurs. If the forward resistance of the diode is negligible compared to R the rms voltage (in volt) across R is approximately
Physics-Semiconductor Devices-87972.png
  • 200
  • 100

  • Physics-Semiconductor Devices-87973.png
  • 280
The junction diode in the following circuit requires a minimum current of 1 mA to be above the knee point (0.7 V) of its I-V characteristic curve. The voltage across the diode is independent of current above the knee point. If VB = 5V, then the maximum value of R so that the voltage is above the knee point, will be
Physics-Semiconductor Devices-87975.png
  • 4.3 kΩ
  • 860 kΩ
  • 4.3Ω
  • 860Ω
In the circuit given below, V(t) is the sinusoidal voltage source, voltage drop VAB (t) across the resistance R is
Physics-Semiconductor Devices-87977.png
  • Is half wave rectified
  • Is full wave rectified
  • Has the same peak value in the positive and negative half cycles
  • Has different peak values during positive and negative half cycle
A transistor is used as an amplifier in CB mode with a load resistance of 5 kΩ the current gain of amplifier is 0.98 and the input resistance is 70Ω, the voltage gain and power gain respectively are
  • 70, 68.6
  • 80, 75.6
  • 60, 66.6
  • 90, 96.6
In the following circuits PN-junction diodes D1, D2 and D3 are ideal for the following potentials of A and B. The correct increasing order of resistance between A and B will be
(i) –10V, –5V
(ii) –5V, –10V
(iii) – 4V, –12V

Physics-Semiconductor Devices-87979.png
  • (i) < (ii) < (iii)
  • (iii) < (ii) < (i)
  • (ii) = (iii) < (i)
  • (i) = (iii) < (ii)
The circuit shown in following figure contains two diodes D1 and D2 each with a forward resistance of 50 ohms and with infinite backward resistance. If the battery voltage is 6 V, the current through the 100 ohm resistance (in amperes) is
Physics-Semiconductor Devices-87981.png
  • Zero
  • 0.024
  • 0.03
  • 0.036

Physics-Semiconductor Devices-87983.png
  • 0.25 A
  • 0.45 A
  • 0.56 A
  • 0.64 A

Physics-Semiconductor Devices-87985.png
  • 6 : 5
  • 5 : 6
  • 3 : 2
  • 2 : 3
Ge and Si diodes conduct at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection is reversed, the value of V0 changes by
Physics-Semiconductor Devices-87987.png
  • 0.2 V
  • 0.4 V
  • 0.6 V
  • 0.8 V
In the circuit shown in figure the maximum output voltage V0 is
Physics-Semiconductor Devices-87989.png
  • 0 V
  • 5 V
  • 10 V

  • Physics-Semiconductor Devices-87990.png
In the following circuit I1 and I2Physics-Semiconductor Devices-87992.png
  • 0, 0
  • 5 mA, 5 mA
  • 5 mA, 0
  • 0, 5 mA
For the transistor circuit shown below, if β = 100, voltage drop between emitter and base is 0.7 V, then value of VCE will be
Physics-Semiconductor Devices-87994.png
  • 10 V
  • 5 V
  • 13 V
  • 0 V
In NPN transistor, 1010 electrons enter in emitter region in 10–6 s. If 2% electrons are lost in base region, then collector current and current amplification factor (β) respectively are
  • 1.57 mA, 49
  • 1.92 mA, 70
  • 2 mA, 25
  • 2.25 mA, 100
The following configuration of gate is equivalent to
Physics-Semiconductor Devices-87997.png
  • NAND
  • XOR
  • OR
  • None of these
Figure gives a system of logic gates. From the study of truth table it can be found that to produce a high output (at R, we must have
Physics-Semiconductor Devices-87999.png
  • X = 0, Y = 1
  • X = 1, Y = 1
  • X = 1, Y = 0
  • X = 0, Y = 0
The combination of gates shown below produces
Physics-Semiconductor Devices-88001.png
  • AND gate
  • XOR gate
  • NOR gate
  • NAND gate
The figure shows two NAND gates followed by a NOR gate. The system is equivalent to the following logic gate
Physics-Semiconductor Devices-88003.png
  • OR
  • AND
  • NAND
  • None of these
The diagram of a logic circuit is given below. The output F of the circuit is represented by
Physics-Semiconductor Devices-88005.png

  • Physics-Semiconductor Devices-88006.png
  • 2)
    Physics-Semiconductor Devices-88007.png

  • Physics-Semiconductor Devices-88008.png

  • Physics-Semiconductor Devices-88009.png
The plate current ip in a triode valve is given ip = K(Vp + µVg)3/2, where ip is in milliampere and Vp and Vg are in volt. If rp =104 ohm and gm = 5 × 10–3 mho, then for ip = 8 mA and Vp = 300 volt, what is the value of K and grid cut off voltage?
  • –6V, (30)3/2
  • –6V, (1/30)3/2
  • + 6V, (30)3/2
  • + 6V, (1 /30)3/2
The linear portions of the characteristic curves of a triode valve give the following readings
The plate resistance is
Physics-Semiconductor Devices-88012.png
  • 2000 ohms
  • 4000 ohms
  • 8000 ohms
  • 6000 ohms
The relation between dynamic plate resistance (rp) of a vacuum diode and plate current in the space charge limited region, is

  • Physics-Semiconductor Devices-88014.png
  • 2)
    Physics-Semiconductor Devices-88015.png

  • Physics-Semiconductor Devices-88016.png

  • Physics-Semiconductor Devices-88017.png
An alternating voltage of 141.4 V (rms) is applied to a vacuum diode as shown in the figure. The maximum potential difference across the condenser will be
Physics-Semiconductor Devices-88019.png
  • 100 V
  • 200 V
  • 100√2V
  • 200√2V
A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission current of 1 mA. If another metallic surface having the same surface area, same emission constant but work function 4 eV is heated to a temperature of 1600 K, then the emission current will be
  • 1 mA
  • 2 mA
  • 4 mA
  • None of these
A change of 0.8 mA in the anode current of a triode occurs when the anode potential is changed by 10 V. If µ = 8 for the triode, then what change in the grid voltage would be required to produce a change of 4 mA in the anode current
  • 6.25 V
  • 0.16 V
  • 15.2 V
  • None of these
The plate current in a triode is given by
Ip = 0.004(Vp + 10Vg)3/2 mA
where Ip\' Vp and Vg are the values of plate current, plate voltage and grid voltage, respectively. What are the triode parameters µ, rp and gm for the operating point at Vp = 120 volt and Vg = –2 volt
  • 10, 16.7 kΩ, 0.6 m mho
  • 15, 16.7 kΩ, 0.06 m mho
  • 20, 6 kΩ, 16.7 m mho
  • None of the above
A triode whose mutual conductance is 2.5 m A/volt and anode resistance is 20 kilo ohm, is used as an amplifier whose amplification is 10. The resistance connected in plate circuit will be
  • 1 KΩ
  • 5 KΩ
  • 10 KΩ
  • 20 KΩ

Physics-Semiconductor Devices-88025.png
  • 1.27 mA
  • 10 mA
  • 1.5 mA
  • 12.4 mA
The slopes of anode and mutual characteristics of a triode are 0.02 mA V–1 and 1 mA V–1 respectively. What is the amplification factor of the valve?
  • 5
  • 50
  • 500
  • 0.5
Amplification factor of a triode is 10. When the plate potential is 200 volt and grid potential is –4 volt, then the plate current of 4 mA is observed. If plate potential is changed to 160 volt and grid potential is kept at –7 volt, then the plate current will be
  • 1.69 mA
  • 3.95 mA
  • 2.87 mA
  • 7.02 mA
On applying a potential of –1 volt at the grid of a triode, the following relation between plate voltage Vp (volt) and plate current Ip (in mA) is found Vp = 0.125Vp – 7.5 If on applying –3 volt potential at grid and 300 V potential at plate, the plate current is found to be 5 mA, then amplification factor of the triode is
  • 100
  • 50
  • 30
  • 20
In the circuit given the current through the zener diode is
Physics-Semiconductor Devices-88030.png
  • 10 mA
  • 6.67 mA
  • 5 mA
  • 3.33 mA
  • 0 mA
0:0:1


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