Analog Electronics – Diodes and Applications

Fill-in-the-blank flashcards covering key concepts of semiconductor diodes, their characteristics, rectifiers, filters, voltage regulators, and special-purpose diodes from the lecture notes.

A __ is an electronic device that allows current to flow in one direction and blocks it in the opposite direction.

Diode

The region around the PN junction that lacks mobile carriers is called the __ region.

depletion (space-charge) region

The built-in voltage opposing carrier diffusion across a PN junction is known as the __ potential.

barrier potential

For silicon, the typical barrier potential at room temperature is about __ V.

0.7 V

For germanium, the barrier potential is approximately __ V.

0.3 V

Applying external voltage across a diode is referred to as __.

biasing

When the P-type is connected to positive and N-type to negative, the diode is under __ bias.

forward

Under forward bias a diode behaves like a(n) __ switch.

closed (ON)

In reverse bias, the small current due to minority carriers is called the __ current.

reverse saturation current (I0 or IS)

The sudden rise in reverse current at a certain reverse voltage is called the __ voltage.

breakdown voltage

In the diode symbol, the arrow points in the direction of __ flow (conventional current).

hole

The forward IV curve point where current starts increasing sharply is called the __ point.

knee (cut-in) point

The reverse saturation current of a diode approximately doubles for every __ °C rise in temperature.

10

The ratio VD/ID at a particular operating point gives the diode’s __ resistance.

static (DC)

The small-signal or dynamic resistance equals the __ of the IV curve at the operating point.

slope (ΔV/ΔI, derivative)

An ideal diode has forward resistance and reverse resistance .

zero; infinite

A practical silicon diode shows an approximate forward knee voltage of __ V.

0.7 V

The two main breakdown mechanisms in diodes are breakdown and breakdown.

Zener; avalanche

A heavily doped diode designed to operate in breakdown at a precise voltage is called a __ diode.

Zener

A diode whose junction capacitance varies with reverse voltage is known as a __ diode.

varactor (varicap)

In a basic DC power supply, the component that lowers the AC mains voltage and provides isolation is the __.

step-down transformer

The block that converts an AC waveform into a unidirectional pulsating DC is the __.

rectifier

A half-wave rectifier uses __ diode(s).

one

A center-tapped full-wave rectifier requires __ diodes.

two

A bridge rectifier needs __ diodes.

four

For a half-wave rectifier, the diode’s PIV must exceed __.

Vm (peak secondary voltage)

For a center-tapped full-wave rectifier, each diode must withstand a PIV of __.

2 Vm

For a bridge rectifier, the required PIV per diode is __.

Vm

The ratio of the rms AC component to the DC component in rectifier output is the __ factor.

ripple

A filter capacitor reduces ripple because it during voltage peaks and during valleys.

charges; discharges

For a given frequency, increasing the product C × RL will __ the ripple factor.

decrease

A voltage regulator maintains a nearly constant __ across the load.

DC output voltage

In a Zener shunt regulator, the series resistor must allow at least __ current through the Zener when Vin is minimum.

IZ(min)

In the 78XX regulator series, the ‘05’ in 7805 denotes a fixed output of __ V.

5

79XX IC regulators provide fixed __ (positive/negative) voltages.

negative

The LM317 adjustable regulator can supply up to about __ A.

1.5 A

An LED emits light when it is __ biased.

forward

Materials such as GaAs used in LEDs often emit light in the __ range.

infrared

A photodiode is normally operated in __ bias to detect light.

reverse

A device that optically couples an LED and a photosensor to isolate circuits is called an __.

optocoupler (opto-isolator)

A solar cell converts light energy directly into electricity via the __ effect.

photovoltaic

The open-circuit voltage of a single silicon solar cell is typically about __ V.

0.5–0.6 V

Connecting many solar cells in series forms a __.

solar panel (array)

In a common-anode seven-segment display, the individual segments are __ diodes.

LED

Reverse saturation current in diode equations is symbolised by __.

I0 (or IS)

The diode equation ID = I0 (e^{VD/ηVT} – 1) expresses current as an exponential function of __.

junction voltage (VD)

For silicon diodes, the ideality factor η is typically __.

2

Rectifier efficiency is defined as DC output power divided by __.

AC input power

Even after filtering, the small AC component superimposed on the DC output is called __.

ripple

Varactor diodes are widely used in __ circuits to electronically tune resonant frequency.

tuning (e.g., VHF/UHF, FM)