Tamil Nadu HSE First Year Basic Electronics Engineering key terms

The rate at which electric charge flows past a point in a circuit, measured in amperes. One ampere equals one coulomb of charge passing per second in a steady flow.

The work needed to move unit positive charge between two points in a circuit, measured in volts. It is the electrical 'push' that drives current through a component.

The energy supplied per unit charge by a source such as a battery or generator, expressed in volts. It is the open-circuit voltage available before internal resistance causes any drop.

The opposition a material offers to current flow, measured in ohms. It depends on the material's resistivity, its length, its cross-sectional area and its temperature.

For a conductor at constant temperature, the current through it is directly proportional to the voltage across it. Written as V = IR, it links voltage, current and resistance in simple circuits.

The total current entering a junction equals the total current leaving it, because charge cannot accumulate at a node. It expresses conservation of charge in any network.

Around any closed loop in a circuit, the algebraic sum of all voltage rises and drops is zero. It expresses conservation of energy for the charges travelling round the loop.

A connection in which components form a single path so the same current passes through each one. Total resistance is the sum of the individual resistances and the supply voltage divides among them.

A connection in which components share the same two nodes, so each has the full supply voltage across it while the current divides between branches. Total resistance is always less than the smallest branch resistance.

The small resistance present inside any real source, such as a cell, which causes its terminal voltage to fall as the current drawn increases. It limits the maximum current a source can deliver.

A property of a material, measured in ohm-metres, giving the resistance of a unit length with unit cross-section. Copper has low resistivity; nichrome has high resistivity and is used for heating elements.

A standard scheme in which coloured bands on a resistor body encode its value and tolerance. The first two bands give digits, the third gives the multiplier, and a fourth or fifth band gives tolerance.

The permitted variation of a component's actual value from its marked value, usually stated as a percentage. A 100 ohm resistor with 5 percent tolerance may lie between 95 and 105 ohms.

A three-terminal resistor with a sliding contact that taps off an adjustable fraction of the applied voltage. It is used as a volume control or as a variable voltage divider in circuits.

A component that stores energy in an electric field between two conducting plates separated by a dielectric. Its capacitance, measured in farads, is the charge stored per volt applied.

The insulating material between capacitor plates, such as air, ceramic, polyester or electrolytic film. Its permittivity determines how much capacitance a given plate area and spacing can provide.

The opposition a capacitor offers to alternating current, equal to one divided by two pi times frequency times capacitance. It falls as frequency rises, so a capacitor blocks DC but passes AC.

A coil that stores energy in a magnetic field when current flows through it, with inductance measured in henries. It opposes changes in current and passes DC while opposing AC.

The opposition a coil offers to alternating current, equal to two pi times frequency times inductance. It increases with frequency, which is why a choke smooths ripple in a supply.

Two or more resistors in series across a supply, where the voltage across one resistor is a fixed fraction of the total. It is widely used to bias transistor bases and set reference levels.

The boundary formed when p-type and n-type semiconductor material meet, creating a depletion region with a built-in potential barrier. It conducts easily in one direction and blocks the other.

The thin zone at a PN junction where mobile carriers have diffused away, leaving fixed ionised atoms and therefore no free charge. Its width changes with applied bias and sets the junction's behaviour.

The small voltage, about 0.7 V for silicon and 0.3 V for germanium, needed before a forward-biased junction conducts appreciably. It arises from the built-in field across the depletion region.

A two-terminal semiconductor device with a PN junction that conducts conventional current from anode to cathode when forward biased and blocks it when reverse biased. It is used for rectification, protection and clipping.

A circuit that converts alternating current into pulsating direct current using one or more diodes. Half-wave types use one diode; full-wave and bridge types use two or four.

The ratio of the alternating component in a rectifier's output to its direct component, indicating how smooth the output is. Lower values mean better smoothing, typically after a filter capacitor.

A heavily doped diode designed to operate safely in reverse breakdown at a specified voltage. Biased in reverse with a series resistor, it holds a steady voltage and serves as a simple regulator.

A three-terminal device with emitter, base and collector regions in which a small base current controls a much larger collector current. It comes in NPN and PNP types and is used for amplification and switching.

The ratio of collector current to base current in a transistor, denoted beta or hFE in common-emitter configuration. Values typically range from about 50 to 500 for small-signal devices.

Setting the steady direct currents and voltages at a transistor's terminals so it sits at a suitable operating point. Proper bias keeps the device in the active region and prevents distortion or thermal runaway.

The collector current and collector-emitter voltage that exist when no signal is applied, often called the Q-point. Its position on the load line determines the maximum undistorted output swing.

A transistor circuit in which the emitter is shared between input and output, giving high voltage gain and a 180-degree phase inversion. It is the most widely used small-signal amplifier configuration.

A voltage-controlled device in which an electric field applied to a gate modulates the current flowing through a channel between source and drain. It draws almost no gate current, giving very high input impedance.

A field effect transistor whose gate is insulated from the channel by a thin oxide layer, so the gate draws negligible current. It is the standard switching device in power supplies and digital circuits.

A four-layer latching semiconductor switch that starts conducting when a gate pulse is applied and continues until the current falls below a holding level. It is used for phase control of AC power.

A basic digital circuit that produces one defined output for each combination of binary inputs. Common types are AND, OR, NOT, NAND, NOR, XOR and XNOR, described by truth tables.

A table listing every possible combination of input logic levels alongside the resulting output for a gate or circuit. It completely defines the behaviour of a combinational logic function.

A set of rules for manipulating binary variables using operations AND, OR and NOT. It allows logic expressions to be simplified before implementing them with gates, reducing component count.

A high-gain differential amplifier supplied as an integrated circuit, usually with very high input impedance and low output impedance. With external feedback it performs amplification, summing, integration and comparison.

Returning a fraction of the output signal to the inverting input so that it opposes the input. It reduces gain but improves stability, bandwidth, linearity and input impedance of an amplifier.

The condition in an ideal inverting op-amp circuit where feedback holds the inverting input at almost the same potential as the non-inverting input, effectively zero volts, without a real connection to ground.

A measuring instrument that plots signal voltage against time on a fluorescent screen, allowing waveform shape, amplitude, frequency and phase to be observed directly.

A combined instrument that measures voltage, current and resistance, available in analogue and digital forms. A digital multimeter displays readings numerically and usually offers a diode and continuity test.

The process of varying a property of a high-frequency carrier wave in step with an information signal. Amplitude, frequency and phase are the properties commonly varied.

A modulation scheme in which the amplitude of a radio-frequency carrier is varied in proportion to the audio or data signal, while its frequency stays fixed. It is simple but susceptible to noise.

Joining metal surfaces with a low-melting-point alloy that wets both parts and solidifies to form an electrical and mechanical bond. Clean surfaces, correct heat and a little flux give a bright, reliable joint.

A soldered connection where the solder has not properly wetted the surfaces, leaving a dull, grainy, high-resistance contact. It usually results from insufficient heat, dirt or movement while cooling.

An insulating board with copper tracks etched in place of wires to connect components. Components are inserted or surface-mounted and soldered to pads, giving compact, repeatable and reliable assemblies.