Maharashtra HSC Electronics Technology (Vocational) key terms

A thin zone at a PN junction where mobile electrons and holes have diffused away, leaving fixed charged ions. It creates a built-in potential barrier that must be overcome before current can flow.

Connecting the P side of a junction to the positive supply and the N side to the negative, which narrows the depletion region and allows substantial current to flow once the knee voltage is exceeded.

A controlled reverse breakdown in a heavily doped diode where a strong electric field frees carriers, giving a nearly constant breakdown voltage used for reference and regulation purposes.

A field-effect transistor whose metal-oxide-semiconductor gate is insulated from the channel, so almost no gate current flows. Gate voltage controls channel conductivity, making it useful for switching and power control.

A resistor whose resistance changes strongly with temperature. NTC types fall in resistance as they warm, which suits temperature sensing, inrush current limiting, and simple compensation networks.

The opposition a capacitor offers to alternating current, equal to one divided by two pi times frequency times capacitance. It falls as frequency or capacitance rises, so capacitors pass high frequencies and block DC.

The condition in an LC network where inductive and capacitive reactances are equal and cancel, leaving only resistance. Series circuits show minimum impedance; parallel circuits show maximum impedance at that frequency.

A capacitor placed between two circuit stages to pass the AC signal while blocking DC bias. Its reactance must be small at the lowest signal frequency of interest.

The ratio of the AC ripple voltage to the DC output voltage of a rectifier supply, usually quoted as a percentage. Lower values mean smoother, better-filtered direct current.

A four-diode full-wave rectifier that conducts on both halves of the AC cycle without needing a centre tap. It gives twice the ripple frequency and better transformer utilisation than a half-wave circuit.

A circuit that holds its output voltage nearly constant despite changes in input voltage or load current. Linear types dissipate excess power as heat; switching types are far more efficient.

A large capacitor connected across a rectifier output that charges near the peak voltage and discharges slowly into the load, reducing ripple between successive charging pulses.

Returning a fraction of the output signal to the input in opposite phase. It lowers gain but improves bandwidth, linearity, input impedance, and stability of an amplifier.

An amplifier stage in which each transistor conducts for half the signal cycle and a matched pair combines the halves. Efficiency is high, but crossover distortion appears near zero volts.

Conditions for sustained oscillation: the loop gain magnitude must equal one and the total phase shift around the feedback loop must be zero or a whole multiple of 360 degrees.

An LC oscillator that uses a tapped capacitive divider to feed a portion of the output back to the input, with the inductor and two capacitors setting the frequency of oscillation.

A table listing every possible combination of input logic levels for a gate or circuit alongside the resulting output, used to verify or design its logic function.

Two identities of Boolean algebra: the complement of a product equals the sum of the complements, and the complement of a sum equals the product of the complements.

A bistable digital storage element with two stable output states that holds one bit until a clock or input changes it. Common forms include SR, D, JK, and T.

A grid arrangement of truth table cells, ordered by Gray code, that lets adjacent ones be grouped visually to simplify Boolean expressions with far less algebraic manipulation.

A number describing how strongly a carrier is varied by the modulating signal. In amplitude modulation it is the ratio of modulating amplitude to carrier amplitude; values above one cause overmodulation.

The range of frequencies a system passes or occupies, usually the difference between upper and lower cut-off frequencies. It limits how much information a channel can carry.

The rule that a band-limited signal must be sampled at more than twice its highest frequency to be reconstructed without aliasing. Practical designs add a guard band above this minimum.

Sharing one communication channel among several signals by separating them in time, frequency, or code. It cuts the cost of transmission paths and underpins telephony and data links.

General-purpose input/output pins on a microcontroller whose direction and logic level are set by software, letting the chip read switches or drive LEDs and relays directly.

A hardware or software signal that pauses the main program, runs a short service routine, then returns to where it stopped. It lets a microcontroller respond quickly without continuous polling.

A circuit that samples an analog voltage and produces a binary number proportional to it. Resolution in bits and conversion time define its accuracy and speed.

A counter that the firmware must periodically reset. If the program hangs, the counter overflows and forces a reset, restoring normal operation without manual intervention.

The error caused when a measuring instrument draws current from the circuit under test, lowering the very voltage it should measure. High input impedance greatly reduces this error.

An instrument that plots voltage against time on a phosphor screen. Vertical deflection shows amplitude and horizontal deflection shows time, letting waveform shape, frequency, and phase be observed.

The smallest change in a measured quantity that an instrument can display or detect. It differs from accuracy, which describes how close a reading is to the true value.

A chemical that removes oxide and prevents re-oxidation during soldering, helping molten solder wet and bond to pads and leads. Residues may need cleaning to avoid later corrosion.

A dull, grainy connection caused by too little heat, movement during cooling, or contaminated surfaces. It looks poor and gives intermittent, high-resistance contact in service.

The minimum gap between copper features, or between copper and board edges, set by voltage, manufacturing limits, and safety standards to prevent arcing and accidental shorts.

The printed legend layer on a circuit board showing component outlines, reference designators, and polarity marks to guide assembly, inspection, and repair work.

A protective polymer coating applied over the board that covers copper areas except the pads, preventing solder bridges between tracks and slowing oxidation during storage and assembly.