Maharashtra HSC Electronics (Bifocal) key terms

A passive component that opposes the flow of electric current and converts electrical energy into heat. Its value is measured in ohms and marked by a colour code on the body.

A passive component that stores electric charge between two conducting plates separated by a dielectric. It blocks steady direct current while allowing alternating current to pass, and its value is measured in farads.

A coil of wire that stores energy in a magnetic field when current flows through it. It opposes changes in current and its value is measured in henries.

A standard system of coloured bands printed on a resistor to indicate its resistance value and tolerance. Each colour represents a digit, a multiplier, or a tolerance figure.

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

The relationship stating that current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance, written as V equals I times R.

A circuit of two or more resistors in series across a supply, used to obtain a smaller voltage at a tapping point. The output voltage is proportional to the resistance below the tap.

An insulating material placed between the plates of a capacitor. It increases capacitance by reducing the electric field strength and prevents direct conduction between the plates.

The boundary formed where p-type and n-type semiconductor materials meet. It allows current easily in one direction and blocks it in the other, forming the basis of the diode.

A thin zone around a PN junction that is depleted of free charge carriers, leaving fixed ions. It acts as a barrier to current flow until an external voltage overcomes it.

The small voltage, about 0.7 volts for silicon and 0.3 volts for germanium, needed to overcome the depletion region before a diode conducts strongly in forward bias.

The condition where the positive supply terminal is connected to the p-side of a diode, lowering the barrier and allowing a large current to flow with a small voltage drop.

The condition where the positive terminal is connected to the n-side of a diode, widening the depletion region and permitting only a very small leakage current to flow.

A diode designed to operate safely in reverse breakdown at a specified voltage. It is used to provide a stable reference voltage or to protect circuits against overvoltage.

A circuit that converts alternating current into direct current using one or more diodes. Half-wave and full-wave forms are common, the latter often built as a bridge.

The small alternating variation remaining in the output of a power supply after rectification and filtering. It is reduced by larger filter capacitors or by a regulator stage.

A three-terminal semiconductor device with emitter, base and collector regions, in which a small base current controls a larger collector current. It exists in NPN and PNP types.

The ratio of collector current to base current in a bipolar transistor, denoted beta or hFE. It indicates how strongly the device amplifies current in the common-emitter configuration.

The arrangement of resistors and supply voltages that sets a transistor's quiescent operating point so it stays in the active region and amplifies without distortion.

A transistor in which an electric field applied to a gate controls the current flowing through a channel between source and drain. It draws almost no gate current.

The ratio of change in drain current to change in gate-source voltage for a field effect transistor. It measures how effectively the gate voltage controls channel current.

A straight line drawn on the output characteristics of a transistor showing all possible combinations of voltage and current set by the external load. Its intersection with the characteristic curve gives the operating point.

The method of passing a signal from one amplifier stage to the next while blocking direct current, usually by a capacitor or a transformer.

Returning a fraction of the output signal to the input in opposite phase. It reduces gain but improves stability, bandwidth, and freedom from distortion in an amplifier.

A circuit that generates a continuous alternating output without an external input signal, using positive feedback and a resonant or phase-shifting network to set the frequency.

An oscillator whose frequency is fixed by a quartz crystal vibrating at its natural resonant frequency. It gives far greater frequency stability than inductor-capacitor or resistor-capacitor types.

A high-gain integrated amplifier with two inputs, inverting and non-inverting. With external resistors it performs amplification, summing, integration and comparison functions.

A basic digital circuit that produces one output state from one or more input states according to a fixed rule. AND, OR, NOT, NAND, NOR and XOR are the standard types.

A table listing every possible combination of inputs to a logic circuit alongside the resulting output. It completely describes the behaviour of a gate or combination of gates.

A system of mathematical rules for manipulating binary variables using operations AND, OR and NOT. It is used to simplify logic expressions before building circuits.

A bistable digital circuit that stores one bit of data and retains it until a clock or input changes it. It forms the basic building block of registers and counters.

A group of flip-flops connected together to store a multi-bit binary word. It may also shift its contents left or right, as in a shift register.

A circuit or integrated device that holds its output voltage nearly constant despite changes in input voltage or load current. Common types are series, shunt and three-terminal regulators.

A network of capacitors, inductors or resistors that removes unwanted frequencies from a signal, such as smoothing the pulsating output of a rectifier into steadier direct current.

A measuring instrument that combines voltmeter, ammeter and ohmmeter functions in one unit. Digital types display readings numerically and usually offer a continuity test.

An instrument that displays a signal as a graph of voltage against time on a screen. Controls adjust time base and vertical sensitivity to measure amplitude, period and waveform shape.

The process of varying a property of a high-frequency carrier wave, such as amplitude or frequency, in accordance with a lower-frequency information signal so it can be transmitted.

The recovery of the original information signal from a modulated carrier wave at the receiver. It reverses the modulation process performed at the transmitter.

A conducting structure that radiates a high-frequency electrical signal into space as electromagnetic waves, or intercepts such waves and converts them back into electrical signals.

A single integrated circuit containing a processor, memory and input/output peripherals. It is programmed to control devices and is widely used in embedded consumer products.

A dedicated computer built into a larger device to perform a specific control task, such as operating a washing machine or an air conditioner, rather than general-purpose computing.

Software permanently stored in read-only or flash memory of a microcontroller that controls the device's basic operation and is rarely changed by the user.

A method of joining metal parts by melting a low-melting-point alloy onto them. Good joints are bright and smooth, and surfaces must be clean and heated before solder is applied.

A soldered connection where the solder has not properly wetted or bonded to the metal, giving a dull, rough appearance and an unreliable, high-resistance electrical contact.

An insulating board with thin copper tracks etched on its surface, used to mount and interconnect electronic components. It replaces most hand wiring in modern equipment.

A hand tool that sucks molten solder away from a joint so a component can be removed or a faulty connection reworked without damaging the board.

Connecting exposed metal parts of equipment to the ground so that a fault current flows safely to earth and protective devices operate, reducing the risk of electric shock.

A deliberately weak link in a circuit that melts and breaks the current path when the current exceeds its rating, protecting wiring and components from overheating.