amplifier: a device which increases the amplitude of a voltage and/or current.

analog: a continuously changing quantity as opposed to the on-off signals used in digital electronics.

Anode: the positive terminal of a diode.

atom:  the basic building block of all matter. It consists of a nucleus made up of protons and neutrons, surrounded by electrons. Atoms often bond with atoms of other elements to form molecules.

atomic number:  the number of protons in an element; each element has a unique atomic number.

atomic structure:  the arrangement of sub-atomic particles within an atom.

barrier voltage: the voltage difference which arises between adjacent N-type and P-type semiconductor layers.

base: the central layer of a bipolar transistor. The current through the base controls the collector current.

base current: the current flowing between the emitter and the base in a bipolar transistor.

bias:  the polarity and amplitude of voltage applied to a semiconductor device, which determines its operating characteristics.

Bipolar transistors:  one of the earliest types of transistors, it consists of a layer of N-type or P-type semiconductor sandwiched between two layers of the opposite type. The current through the centre layer, the base, controls the working current.

Bohr model: a model of the structure of the atom developed by Niels Bohr in 1913. It has since been proven that electrons, protons and neutrons are made up of smaller particles, but his model is adequate for explaining electrical circuits.

breakdown voltage: the voltage level which causes a diode to begin conducting in the reverse direction.


Capacitor: a device which can temporarily hold an electrical charge. It consists of a dielectric sandwiched between two conductive plates. The charge is stored in the dielectric.

Capacitance: a measure of the amount of charge which a capacitor can hold. The unit of capacitance is the Farad.

cathode: the negative terminal of a diode.

Chip: integrated circuit.

CMOS: a type of transistor technology which uses matched pairs of P-channel and N-channel MOS transistors.

collector: one terminal of a bipolar transistor. The working current of the transistor passes though the collector.

collector current: the current which passes through the collector of the transistor. It is controlled by the base current.

Complimentary Metal Oxide Semiconductor: see CMOS

conductor: 1. an element which conducts electricity. 2. the component of an electrical circuit which forms the path for electrical current.

Conventional Current: before the discovery of the electron, electricity was described as flowing from positive to negative. This is now known as conventional current. In fact, negatively charged electrons move from the negative terminal to the positive terminal of the power source.

covalent bond: the connection formed between atoms with less than 8 electrons in the outer shell in which valence electrons are shared.

crystalline: a material in which the atoms are arrayed in a regular, repeating, three-dimensional pattern.

Current: the movement of electrical charges.

current gain: the measure of the amplification of current in a circuit, calculated as the ratio between the output current and the input current.

cutoff:  the state of a transistor when the control voltage is too low to turn it on.


Depletion Modea FET transistor is operating in depletion mode when the gate voltage is repels the carrier charges.

dielectric: an insulating material, used to store charges in a capacitor.

Digital: a class of electronic circuits where binary data is stored represented by high or low voltages.  

Diode: a semiconductor device consisting of two layers – an N-type layer (cathode) and a P-type layer (anode). It conducts electricity in only one direction, from cathode to anode (electron flow).

discrete transistor: a single transistor assembled in a case with three leads.

donor element: in semiconductor manufacturing, elements with 5 valence electrons which are added to pure silicon or germanium to create N-type semiconductor.

doping: the process of adding donor or acceptor elements to pure silicon in the manufacture of semiconductor devices.

drain: a terminal on a Field Effect Transistor.


electron: a subatomic particle with a negative charge; in electrical circuits, it is the movement of electrons which creates electrical current.

Electron Current: The flow of electrons from the negative terminal to positive the terminal of the power source in an electrical circuit. (See also conventional current.)

element: a material made up only of atoms with the same atomic number.

emitter: one terminal of a bipolar transistor.

Enhancement Mode: a MOSFET transistor is operating in enhancement mode when the gate voltage attracts the carrier charges, although no current flows through the gate because it is insulated from the carrier channel.

Fab: see Fabrication plant.

fabrication plant: a factory for the manufacture of semiconductor devices.

Farad: the unit of capacitance. A capacitor capable of holding one Coulomb of charge has a capacitance of one Farad. Most capacitors are rated in microfarads (one-millionth of a Farad).

forward Bias: voltage applied to an electronic device with the correct polarity to cause current to flow.

gain: the measure of amplification in an electronic circuit.

gate voltage: the control voltage applied to the gate terminal of a Field Effect Transistor.

germanium: one of the elements classified as semiconductors, used in the manufacture of diodes and transistors.


Holes:  in semiconductor electronics, the unoccupied spaces for valence electrons in P-type semiconductor.

insulators: materials which have a high resistance to the flow of electricity.

integrated circuit: a semiconductor device in which several transistors, resistors and other devices are manufactured on one chip of silicon.

JFET: Junction Field Effect Transistor

Junction Field Effect Transistor: a class of transistors designed so that the gate terminal is always reverse-biased; more efficient than bipolar transistors, since virtually no current flows through the gate.

LED: Light Emitting Diode

Light Emitting Diode: a diode designed to give off light when current flows through it.

linear electronics: the field of analog electronics, in which transistors are used as amplifiers. Linear electronics are used in communications, audio and video equipment, and similar applications.

Metal Oxide Semiconductor Field Effect Transistor: a Field Effect Transistor in which the Metal of the gate terminal is insulated from the Semiconductor of the current channel by a layer of silicon Oxide.

MOSFET: Metal Oxide Semiconductor Field Effect Transistor


n-channel: in an N-channel MOSFET, the N-type semiconductor which connects the source and drain.

neutrons: particles found in the nucleus of an atom which have no electrical charge.

NPN transistors: bipolar transistors manufactured with a thin layer of P-type semiconductor (the base) sandwiched between two layers of N-type semiconductor.

n-type semiconductor: semiconductor doped with donor elements which creates free electrons to act as current carriers.  

nucleus: the centre of an atom, made up of electrically neutral particles called neutrons and positively charged particles called protons.

p-channel in a P-channel MOSFET, the P-type semiconductor which connects the source and drain.

Parallel circuit: an electrical circuit in which the components are arranged so that there is more than one path for current to flow.

Photodiode: a diode which conducts when exposed to light.

PN junction: the region where P-type and N-type semiconductor meet.

PNP transistors: bipolar transistors manufactured with a thin layer of N-type semiconductor (the base) sandwiched between two layers of P-type semiconductor.

power gain: measure of the increase of power produced by an amplifier.

protons: particles found in the nucleus of an atom which have a positive electrical charge.

p-type semiconductor: semiconductor doped with acceptor elements which creates holes into which free electrons can move.


Rectifier: a device made up of one or more diodes, which changes Alternating Current (AC) into Direct Current (DC).

Resistors: devices designed to resist the flow of current in an electrical circuit. In integrated circuits, resistors of different values are manufactured by controlling the level of doping in N-type semiconductor.

reverse bias: voltage applied to an electronic device with polarity opposite to forward bias, so that no current flows.

saturation: when a transistor is operating at its maximum conductivity, it is said to be in saturation.

semiconductor: the elements germanium and silicon. At low temperatures they are insulators, but conductivity increases as they are heated.  

series circuit: an electrical circuit in which the components are arranged so that there is only one path for the current to follow.

shell: one of several energy levels at which the electrons orbiting the nucleus of an atom can be found.

silicon: the most common semiconductor element, used in the manufacture of diodes and transistors.

silicon oxide or Silicon dioxide: the compound produced when silicon reacts with oxygen. It is used as an insulator and a protective covering in the manufacture of semiconductor devices.

source: one of the terminals on a Field Effect Transistor.


Transistor:  a semiconductor device with three terminals, designed so that a small control voltage can control the  working current through the device. It can be used as an amplifier or as a switch.

vacuum tube: an electronic device with anodes, cathodes and plates encased in a glass cylinder from which the air has been evacuated. The plate voltage controls the working current. Vacuum tube diodes act as rectifiers, triodes and pentodes act as switches or amplifiers.

valence electron: one of up to eight electrons found in the outermost shell of an atom. The valence electrons determine the electrical and chemical characteristics of the atom.

voltage gain: a measure of the increase in voltage produced by an amplifier. The gain is the ratio between the output voltage and the input voltage.