ISRO Scientist/Engineer SC (Electronics) key terms

The rise in a MOSFET's threshold voltage when its source terminal is at a higher potential than the body, widening the depletion region and increasing the channel charge needed to invert the surface.

Weak drain current that flows in a MOSFET even when the gate-source voltage is below threshold, because carriers diffuse across the channel; it decays exponentially with gate voltage and limits low-power circuit leakage.

The gate-source voltage at which a MOSFET channel becomes sufficiently conductive to carry a defined drain current, marking the boundary between the cut-off and conducting regions of operation.

The slight widening of a bipolar transistor's base-collector depletion region as collector voltage rises, which narrows the effective base and makes collector current increase with collector-emitter voltage in the active region.

A linear equivalent circuit, built from transconductance and output resistance, that replaces a nonlinear device around a chosen DC operating point so that gains and impedances can be computed with linear analysis.

The multiplication of a feedback capacitance by roughly one plus the stage voltage gain, which makes an inverting amplifier's input capacitance much larger and lowers its bandwidth at high frequencies.

The maximum rate at which an operational amplifier's output voltage can change, usually quoted in volts per microsecond and set by the current available to charge the internal compensation capacitor.

The nearly constant value obtained by multiplying an amplifier's closed-loop gain by its corresponding bandwidth, equal to the unity-gain frequency for a single-pole op-amp response.

Returning a fraction of the output to the input in opposition to the input signal, which stabilises gain, widens bandwidth, reduces distortion and alters input and output impedances.

The difference between the actual loop phase shift and minus 180 degrees at the frequency where loop gain equals unity; it measures how far a feedback system is from instability.

A graphical stability test that counts encirclements of the minus-one point by the open-loop frequency response to determine whether the closed-loop system has right-half-plane poles.

An algebraic test performed on the coefficients of a characteristic polynomial, using an array of rows, to count right-half-plane roots without solving for the roots explicitly.

A rectangular grid in which adjacent cells differ in one input variable, allowing groups of ones to be combined visually into minimal sum-of-products expressions for a Boolean function.

An input combination whose output value is irrelevant because it never occurs or may be chosen freely, letting the designer assign it 0 or 1 to enlarge groupings and simplify logic.

A momentary wrong output in a combinational circuit when one input changes, caused by unequal path delays; it appears as a brief glitch and is removed by adding redundant logic terms.

The minimum interval before the active clock edge during which a flip-flop's data input must remain stable so the correct value is captured; violating it can cause metastability.

The minimum interval after the active clock edge during which a flip-flop's data input must stay stable, ensuring the captured value is not disturbed by the new input arriving too early.

An unresolved output state that can occur when a flip-flop samples data too close to a clock edge, leaving the output between logic levels for an unpredictable time before settling.

The appearance of a signal at a false lower frequency when it is sampled below twice its highest frequency component, causing distinct frequencies to become indistinguishable after sampling.

The minimum sampling frequency, equal to twice the highest frequency present in a band-limited signal, at which the signal can be reconstructed without error from its samples.

A low-pass filter placed before a sampler that attenuates frequency components above half the sampling rate, preventing them from folding back into the desired band as aliases.

A transform that maps a discrete-time sequence into a function of a complex variable, converting convolution into multiplication and enabling stability and frequency analysis of sampled systems.

The set of complex values for which a Laplace or Z transform sum converges; its extent and position relative to poles determine whether the corresponding system is stable and causal.

A mathematical operation that decomposes a signal into the amplitudes and phases of its continuous frequency components, revealing spectral content such as bandwidth and harmonic structure.

A relation stating that the total energy of a signal computed in the time domain equals the energy computed by integrating its spectral density over frequency.

The maximum error-free data rate over a noisy channel, equal to bandwidth times the base-two logarithm of one plus the signal-to-noise ratio, for additive white Gaussian noise.

The ratio of desired signal power to accompanying noise power at a point in a system, usually expressed in decibels and setting the limit on detection and error performance.

The decibel ratio of a receiver's input signal-to-noise ratio to its output signal-to-noise ratio, quantifying how much the device itself degrades the signal's quality.

An equation giving the overall noise factor of cascaded stages as the first stage's factor plus each later stage's factor divided by the gain preceding it, showing that early stages dominate.

The average fraction of transmitted bits received incorrectly over a link, determined by modulation scheme, noise and interference, and used to judge receiver performance.

The ratio of voltage to current for a wave travelling in one direction on a transmission line, fixed by the line's inductance and capacitance per unit length and independent of length.

The complex ratio of reflected to incident wave amplitude at a termination, computed from load and characteristic impedances; its magnitude ranges from zero for a match to one for an open or short.

The ratio of maximum to minimum voltage magnitude along a mismatched line, ranging from one for a perfect match upward as reflections grow stronger.

The distance below a conductor's surface at which current density falls to about 37 percent of its surface value, shrinking as frequency rises and raising effective resistance.

The ratio of an antenna's peak radiation intensity to its average radiation intensity over all directions, describing how well it concentrates energy without regard to losses.

The product of directivity and radiation efficiency, expressing how much more power an antenna radiates in its strongest direction than an ideal isotropic radiator fed the same input power.

The product of transmitter power delivered to the antenna and antenna gain, giving the equivalent power an isotropic radiator would need to produce the same peak flux density.

A link-budget relation giving received power as transmitted power times both antenna gains divided by the square of the distance-to-wavelength ratio, for aligned antennas in free space.

A set of complex ratios describing how much of an incident wave at each port of a microwave network is reflected or transmitted to every other port, measured under matched terminations.