Engineer Electronics key terms

A zone at the boundary between p-type and n-type semiconductor where mobile carriers have diffused away, leaving fixed ionized dopants. It creates a built-in potential barrier that controls current flow and widens under reverse bias.

A reverse-bias conduction mechanism in heavily doped diodes where the strong electric field frees electrons directly from covalent bonds. It occurs at a well-defined low voltage and provides voltage regulation in Zener diodes.

Reverse-bias conduction in which accelerated carriers collide with the lattice and create new electron-hole pairs, multiplying current in a chain reaction. It needs a higher field than Zener breakdown and has a positive temperature coefficient.

The average time a carrier survives in a semiconductor before recombining. It sets the switching speed of bipolar devices and the reverse recovery charge of diodes, since stored minority charge must be removed before the device turns off.

The gate-source voltage at which an inversion layer forms and significant drain current begins to flow. It depends on oxide thickness, doping, and flat-band voltage, and it shifts with temperature and body bias.

The ratio of a small change in output current to the small change in input voltage that causes it, written gm. For a BJT it is Ic/VT; for a FET it is the drain-current slope against gate voltage. It sets amplifier gain.

The increase of MOSFET drain current with drain-source voltage in saturation, caused by the depletion region shortening the effective channel. It appears as a finite output resistance and limits intrinsic voltage gain.

A linearized representation of a nonlinear device around a DC operating point, using resistors, controlled sources, and capacitors. It lets designers compute gain, input and output impedance, and bandwidth with linear circuit analysis.

The maximum rate at which an amplifier output can change, usually quoted in volts per microsecond. It is set by the current available to charge internal compensation capacitance and limits large-signal high-frequency performance.

For an op-amp with a single dominant pole, the constant product of closed-loop gain and the frequency at which that gain falls by 3 dB. It equals the unity-gain frequency and predicts bandwidth for any closed-loop gain.

Returning a fraction of the output to the input so that it opposes the input change. It stabilizes gain, widens bandwidth, reduces distortion and output impedance, and can cause instability if phase shift reaches 180 degrees with sufficient loop gain.

The difference between the loop phase shift and 180 degrees at the frequency where loop gain magnitude equals one. A positive margin of about 45 to 60 degrees gives a stable, well-damped closed-loop response.

A grid layout of a truth table in which adjacent cells differ in one variable, allowing visual grouping of minterms. Grouping powers of two yields a minimized sum-of-products expression for combinational logic.

An input combination whose output is unspecified because it cannot occur or its value is irrelevant. Treating these as either 0 or 1 during minimization can produce simpler logic without changing required behavior.

The intervals before and after a clock edge during which a flip-flop data input must remain stable. Violating either causes metastability; the values are used with clock skew and propagation delay to check timing.

A condition in which a bistable circuit lingers between logic levels for an unpredictable time after a timing violation. It is mitigated by synchronizer flip-flops and by limiting the clock rate or skew.

A bandlimited signal must be sampled at more than twice its highest frequency to be reconstructed without aliasing. Undersampling folds high-frequency content onto lower frequencies, corrupting the recovered signal irreversibly.

The overlap of spectral replicas that occurs when a signal is sampled below the Nyquist rate, making high frequencies appear as false low frequencies. Anti-alias filters placed before the sampler prevent it.

The discrete-time counterpart of the Laplace transform, expressing a sequence as a power series in z. Its region of convergence and pole locations determine stability and frequency response of digital filters.

An operation combining two signals by reversing and shifting one, then integrating or summing the product. In linear time-invariant systems the output is the input convolved with the impulse response, equivalent to multiplication in the frequency domain.

A mathematical operation that decomposes a signal into complex sinusoids, giving amplitude and phase versus frequency. It converts convolution into multiplication and is central to spectrum analysis and filter design.

A statement that the total energy of a signal computed in the time domain equals the energy computed from its Fourier transform. It is used to check transform scaling and to relate power in time and frequency representations.

The output of a linear time-invariant system when excited by a unit impulse. It fully characterizes the system, and its Fourier or Laplace transform gives the frequency response and transfer function.

The ratio of voltage to current for a wave traveling in one direction on a transmission line, equal to the square root of series impedance over shunt admittance. It determines reflections at load terminations.

The complex ratio of reflected to incident wave amplitude at a discontinuity, equal to load impedance minus characteristic impedance over their sum. Its magnitude ranges from zero for a matched load to one for a short or open.

The ratio of maximum to minimum voltage magnitude along a mismatched line, computed from the reflection coefficient magnitude. A value of one means a perfect match; higher values indicate reflected power and possible equipment stress.

The cross product of electric and magnetic field vectors, giving power flow density in watts per square meter. Its time average describes the direction and intensity of energy transport in electromagnetic waves.

The fraction of a switching period during which a switch or pulse is in its active state, usually expressed as a percentage. In a buck converter it approximately equals output voltage divided by input voltage in continuous conduction.

A converter operating state in which the inductor current never falls to zero during a switching cycle. It gives a predictable voltage conversion ratio and lower current ripple than discontinuous mode at the same load.

A technique that varies the on-time of a fixed-frequency switching signal to control average voltage or power. It is used in motor drives, inverters, and DC-DC converters, trading switching loss against ripple.

The ratio of the root-sum-square of harmonic components above the fundamental to the fundamental amplitude, often in percent. It quantifies waveform purity in inverters, amplifiers, and motor drives.

The fractional difference between synchronous speed and actual rotor speed in an induction machine, positive in motoring and negative in generating. It determines rotor frequency, torque, and current drawn from the supply.

The rotational speed of the rotating magnetic field in an AC machine, equal to 120 times frequency divided by pole number. An induction rotor always runs slightly slower, while a synchronous machine locks to this speed.

An algebraic test that determines closed-loop stability from the coefficients of the characteristic polynomial without solving for roots. It counts right-half-plane poles by inspecting the first column of the Routh array.

A pair of graphs showing magnitude in decibels and phase in degrees against logarithmic frequency for a system. It reveals gain and phase margins, crossover frequency, and pole and zero locations.

The residual difference between reference and output as time tends to infinity for a standard input. It depends on system type and error constants, and can be reduced by increasing loop gain or adding integral action.

An addressing scheme in which peripheral registers occupy the same address space as memory and are accessed with ordinary load and store instructions. It simplifies instruction sets but consumes address space.

A table in memory holding the addresses of interrupt service routines, indexed by interrupt number. On an interrupt the processor reads the entry and jumps to the handler, so the table must be correctly initialized.

A controller that moves data between peripherals and memory without per-byte processor involvement, raising an interrupt when finished. It improves throughput for block transfers such as ADC sampling or serial communication.

An iterative root-finding scheme that updates an estimate using the function value divided by its derivative. It converges quadratically near a simple root but can diverge or fail where the derivative is near zero.

A numerical integration formula that approximates area under a curve by summing trapezoids between sample points. Its error is second order in step size, and it is exact for linear integrands.