TIP1123 Chapter 10_Electronics
10.0 Introduction to Electronics
Overview of Chapter 10 focusing on electronics and semiconductors, particularlydiodes.
10.1 Atomic Number
Atomic number (Z): Number of protons in the nucleus of an atom.
Arrangement of elements in the periodic table is based on atomic number.
Neutral atoms have equal numbers of protons and electrons, net charge = 0.
10.2 Electron Shells & Orbit
Bohr Model: Electrons orbit the nucleus at specific, discrete distances known as shells.
Each shell has a maximum number of electrons it can hold; examples include:
Copper: 2, 8, 18, 1
Silicon: 2, 8, 4
10.3 Valence Electrons
Electrons in the outermost shell (valence shell) determine chemical reactions and electrical properties.
Valence electrons are less tightly bound to the atom, contributing to bonding behavior.
10.4 Ionization
When an atom absorbs external energy, valence electrons can gain enough energy to escape from the atom, resulting in ionization.
This leaves a positively charged ion and a free electron.
Conduction
Room temperature, few electrons can acquire enough thermal energy to reach conduction band.
Cause some valence electrons to gain sufficient energy to jump gap from valence band to conduction band (free electrons) Hole is left in valence band
every electron moved to conduction band left 1 hole in valence band = electron hole pair
Free electrons = conduction electrons
Recombination
conduction band electron lose energy and fall back to hole in valence band
10.5 Semiconductors & Semiconductor Materials
Materials classified as:
Conductors: e.g., Copper, aluminum, allows free movement of electric charges.
Insulators: e.g., Glass, rubber, restricts charge movement.
Semiconductors: Exhibit properties intermediate between conductors and insulators, typically made of silicon or germanium.
10.6 Electron & Hole Current
In intrinsic semiconductors, applying voltage allows free electrons in the conduction band to move, producing an electric current.
Hole current occurs when valence electrons move into holes, creating new holes and effectively causing holes to move through the semiconductor.
10.7 Doping
Doping: The process of adding impurities to a pure semiconductor to enhance its conductivity.
Intrinsic: Naturally occurring semiconductors.
Extrinsic: Semiconductors modified by doping.
Types of Doping:
Trivalent Doping (3 valence electrons): Results in p-type semiconductors (e.g., Al, B).
Pentavalent Doping (5 valence electrons): Results in n-type semiconductors (e.g., P, As).
10.8 N-type Semiconductor
Formed by adding pentavalent impurities, increasing the number of conduction electrons (e.g., Phosphorus, Arsenic).
Majority carriers in n-type materials are electrons.
10.9 P-type Semiconductor
Formed by adding trivalent impurities, creating holes (e.g., Boron, Aluminum).
Majority carriers in p-type materials are holes.
Hole conduction densities>electrons
10.10 Diode Basics
Definition: Two-terminal device that conducts current in one direction.
An ideal diode has zero resistance in the forward direction and infinite resistance in reverse.
Diode Functions
Blocks current in one direction and allows it to flow in the opposite direction, protecting circuits (e.g., in battery-operated devices).
Diode Construction
Consists of a pn junction; one half n-type (cathode) and the other p-type (anode).
Diode symbol represents cathode (K) and anode (A).
Resistor: limit forward bias current to not overheat and damage pn junction
Forward and Reverse Bias
Forward Bias: Positive voltage connected to the anode, allowing current flow.
Reverse Bias: Positive voltage connected to the cathode, resulting in minimal current, approximately zero.