Revision Notes for Class 12 Physics Chapter 14 – Semiconductor Electronics

These flashcards cover the key concepts and definitions related to semiconductor electronics, including energy bands, types of semiconductors, diode behavior, and amplification.

What are energy bands in solids?

Energy bands are ranges of permissible energy levels for electrons in solids due to atomic arrangements in a lattice.

Define the valence band.

The valence band is the range of energy levels occupied by valence electrons in a solid.

What is the conduction band?

The conduction band is the range of energy levels that are not fully occupied by electrons and can conduct electricity.

What is the forbidden energy gap?

The forbidden energy gap is the energy range between the valence band and conduction band where no electron states are available.

What are conductors?

Conductors are materials that allow the easy flow of charge carriers.

Define insulators.

Insulators are materials that do not permit the free flow of charge carriers.

What are semiconductors?

Semiconductors are materials that have conductivity between that of insulators and conductors.

What is the characteristic of resistivity in semiconductors?

Semiconductors have less resistivity than insulators and more than conductors.

How does temperature affect semiconductors?

The resistance of semiconductors decreases with increasing temperature.

What are intrinsic semiconductors?

Intrinsic semiconductors are pure semiconductors where electron-hole pairs are generated solely by thermal excitation.

What is doping in semiconductors?

Doping is the addition of impurities to a semiconductor to enhance its electrical conductivity.

What is an N-type semiconductor?

An N-type semiconductor is created by adding pentavalent impurities, resulting in an excess of electrons.

What characterizes a P-type semiconductor?

A P-type semiconductor is made by adding trivalent impurities, leading to an excess of holes as majority carriers.

What is a P-N junction?

A P-N junction is formed when P-type and N-type semiconductors are joined together.

What defines forward bias in a junction diode?

A junction diode is forward biased when the P-side is connected to the positive terminal and the N-side to the negative terminal.

What happens during reverse bias in a junction diode?

During reverse bias, the P-side connects to the negative terminal and the N-side to the positive terminal, preventing current flow.

Define a rectifier.

A rectifier is an electronic device that converts AC power into DC power.

What is the principle of a full wave rectifier?

A full wave rectifier uses both halves of the AC signal to produce a continuous DC output.

What are Zener diodes used for?

Zener diodes are used as voltage regulators due to their ability to conduct in reverse bias.

How does an N-P-N transistor operate?

In an N-P-N transistor, the n-type emitter is forward biased while the n-type collector is reverse biased, controlling current flow.

Define the common emitter amplifier.

A common emitter amplifier has a shared base between the emitter and collector, used for amplifying signals.

What is an analog signal?

An analog signal is a continuous signal that varies over time.

How are digital signals defined?

Digital signals are discrete signals that represent information with two levels, typically 0 and 1.