Unit 4 Notes

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Assignment 3 (BJT)

Q10  Explain the h-Parameter model for 2-port networks. Also, draw and explain the simplified model for Common Emitter Configuration of BJT.

Last Date: 10th April, 2017

Bipolar Junction Transistor Notes

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Zener and Avalanche Breakdown

Zener Breakdown	Avalanche Breakdown
The doping in the formation of P-N junction is High.	The doping in the formation of P-N Junction is low.
The phenomenon is caused by tunneling or field emission. In this the covalent bonds break spontaneously.	The phenomenon is caused by impact ionization and avalanche multiplication. The covalent bonds break as a result of collision of electrons and holes with the valence electrons.
Low reverse potential is required for breakdown	Higher reverse potential is required for breakdown.
In this the covalent bonds near the junction break due to high reverse potential ~20 V and consequently electrons become free.	In this the thermally generated electrons due to electric field ionize other atoms and release electrons.

Comparison of All Rectifiers

Continuity Equation

Assignment 1 (Numerical)

Q1

In an N-type semiconductor, the Fermi level is 0.3 eV below the conduction level at a room temperature of 300 K. If the temperature is increased to 360 K, determine the new position of the Fermi level.

Q2

In a P-type semiconductor, the Fermi level is 0.3 eV above the valance band at a room temperature of 300 K. Determine the new position of the Fermi level for temperatures of (a) 350 K and (b) 400 K.

Q3

In a P-type semiconductor, the Fermi level lies 0.4 eV above the valence band. Determine the new position of Fermi level if the concentration of acceptor atoms is multiplied by a factor of (a) 0.5 and (b) 4. Assume kT = 0.025 eV.

Q4

The electron and hole mobility of Silicon are 0.17 m²/Vs and 0.035 m²/Vs respectively at room temperature. If the current density is known to be 1.1x10¹⁶ per cubic meter, calculate the resistivity of silicon.