Basic Electronics - Diodes and Applications

Comprehensive vocabulary flashcards covering PN junction theory, diode biasing, rectifiers (half-wave, full-wave, bridge), Zener diodes, LEDs, and photodiodes based on the lecture transcript.

PN-junction

The contact surface produced when a p-type semiconductor material is suitably joined to n-type semiconductor material.

Diffusion

The movement of electrons and holes across a junction when N and P-type materials are first brought together, where electrons fill holes to produce negative ions and leave behind positive ions.

Potential Barrier

A zone around the junction area created when a state of equilibrium is reached and electrical charges repel further carriers from crossing the junction.

Depletion Layer

The region around the potential barrier that becomes depleted of any free mobile carriers.

Biasing

The process of connecting an external voltage potential across a semiconductor to enable conduction.

Zero Bias

A condition where no external potential energy is applied to the PN-junction.

Reverse Bias

A condition where a positive voltage is applied to the N-type material and a negative voltage is applied to the P-type material, widening the depletion layer.

Forward Bias

A condition where a negative voltage is applied to the N-type material and a positive voltage is applied to the P-type material, narrowing the depletion layer to allow current flow.

Barrier Potential (Silicon)

The external voltage required to overcome the potential barrier in Silicon, valued at $0.7\,V$.

Barrier Potential (Germanium)

The external voltage required to overcome the potential barrier in Germanium, valued at $0.3\,V$.

Knee voltage (Cut-in Voltage)

The forward voltage at which the diode starts conducting.

Breakdown voltage

The reverse voltage at which the p-n junction breaks down, resulting in a sudden rise in reverse current.

Peak-inverse voltage (PIV)

The maximum reverse voltage that can be applied to a p-n junction without causing damage to the junction.

Maximum Forward current

The maximum instantaneous forward current that a p-n junction can conduct without damaging the junction through overheating.

Zener diode

A heavily doped semiconductor device designed to operate in the reverse direction once the Zener voltage is reached.

Thermal voltage ($V_t$)

The ratio $\frac{kT}{q}$, which at a room temperature of $300\,K$ is approximately $0.02587\,V$ or $25.87\,mV$.

Rectification

The process of converting alternating voltages (AC) to direct voltages (DC).

Half-wave rectifier

A circuit that allows only one half-cycle of an AC input voltage to appear across the load, resulting in pulsating DC.

Rectifier Efficiency ($\eta$)

The ratio of output DC power to the applied input AC power ($\eta = \frac{P_{dc}}{P_{ac}}$).

Maximum Efficiency (Half-wave)

The theoretical maximum efficiency of a half-wave rectifier, which is $40.6\%$..

Maximum Efficiency (Full-wave)

The theoretical maximum efficiency of a full-wave rectifier, which is $81.2\%$..

Bridge rectifier

A type of full-wave rectifier that uses four individual rectifying diodes connected in a bridged configuration and does not require a center-tapped transformer.

Ripple factor ($r$)

The ratio of the RMS value of the AC component (ripple) to the DC component in the rectifier output.

Avalanche Breakdown

A breakdown occurring at high reverse voltages (typically greater than $6\,V$) where free electrons accelerate at high velocities and collide with atoms to knock off more electrons.

Zener Breakdown

A breakdown occurring when a strong electric field in the depletion region pulls electrons directly from their valence band; dominant in voltages up to $5.6\,V$.

Light Emitting Diode (LED)

A diode made from compound semiconductors that emits photons of light when forward current causes electrons from the conduction band to combine with holes from the valence band.

Photodiode

A pn junction device that operates in reverse bias and increases its reverse current in response to light intensity.

Dark current

The negligible reverse current flowing in a photodiode when there is no incident light.

Zener Clipping Circuits

Circuits used to shape or modify an input AC waveform by 'clipping off' excess voltage that exceeds the Zener voltage limit.

Common Cathode Display (CCD)

A 7-segment LED display where all cathode connections are joined together and segments are illuminated by applying a signal to the individual anodes.