JEE HOTS: Semiconductor and Electronics

Semiconductor and Electronics - JEE HOTS

Doping and Semiconductor Properties

• A silicon specimen can be made into a P-type semiconductor by doping, on average, one Indium atom per silicon atom.
• The number density of atoms in the silicon specimen determines the number of acceptor atoms in silicon per cubic centimeter.

Probability of Electrons in Conduction Band

• 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
  • Is not independent of the temperature and the band gap

Ionisation Energy of Donor in Silicon

• The typical ionisation energy of a donor in silicon is 0.05 eV.

PN-Junction Diode

• Reverse saturation current in a PN-junction diode is 10^-12 A at T = 300 K.
• Forward current for a voltage of 0.5 V is 10^-3 A.

Insulator, Semiconductor, and Metal

• Current passing through:
  • An insulator at T = 0 K is zero
  • A semiconductor at T = 0 K is zero
  • A metal at T = 0 K is finite
  • A P-N diode at T = 0 K is finite, if it is reverse biased

Diode Circuits

• Current supplied by the battery when its positive terminal is connected to A is 5 mA.
• If the forward voltage drop for the diode is 0.5 V, the current will be 10 mA.

Acceptor Levels and Hole Creation

• A P-type semiconductor has acceptor levels 57 meV above the valence band.
• The maximum wavelength of light required to create a hole is 2175 nm.

Transistor Amplifier

• Current gain in a transistor amplifier in common emitter configuration is 50.
• Output voltage of the amplifier will be 10 V.

Semiconductor Concentrations and Mobility

• Concentrations of electrons and holes in a semiconductor are 8 × 10^18/m^3 and 5 × 10^18/m^3 respectively.
• Mobilities of electrons and holes are 2.3 m^2/volt-sec and 0.01 m^2/volt-sec respectively.

Half-Wave Rectification

• RMS voltage across R in a half-wave rectification circuit is approximately 141.4 V.

Diode Characteristics

• Voltage across the diode is independent of current above the knee point (0.7 V).
• The minimum current required to be above the knee point is 1 mA.

Transistor Applications

• Voltage gain and power gain in a transistor amplifier in CB mode are 69.7 and 68.25 respectively.

Bohr Radius

• Bohr radius of the fifth electron of phosphorus acting as a dopant in silicon is 1.35 nm.

PN-Junction Diodes in Series

• The correct increasing order of resistance between A and B will be D1, D2, and D3.

Diode Circuits with Capacitors

• The voltage across the capacitor in a diode circuit with a capacitor is 220 V (rms) AC.

Semiconductor Current Flow

• Current flowing through a Ge plate with an applied voltage of 2 V is 2 mA.

Semiconductor Current Components

• Contribution to the total current flowing through a semiconductor due to electrons and holes are 2 mA and 1 mA respectively.

Diode Voltage Drops

• Ge and Si diodes conduct at 0.3 V and 0.7 V respectively.
• Reversing the Ge diode connection changes the value of V0 by 0.4 V.

Logic Gates

• The combination of gates shown produces a NOR gate.
• The system is equivalent to the following logic gate: NAND.
• The output F of the circuit is represented by F = A + BC.
• The diagram of a logic circuit produces an output F = AB + C.

Practice questions on doping, semiconductor properties, and electron probability in conduction band for JEE HOTS exam.