Circ Ctrl & Protectn, Semicond - Week 2

PN junction diode allows current to flow in

one direction only

Si barrier potential

0.7V

Ge barrier potential

0.3V

Current only flows if the external voltage

is greater than the barrier potential

Forward bias

polarity of the voltage source and the diode are matching

Reverse bias

polarity of the voltage source and the diode are not matching

longer line in a voltage source symbol represents

positive

shorter line in a voltage source symbol represents

negative

triangle in a diode symbol represents

anode (positive)

line in a diode symbol represents

cathode (negative)

When using an ohmmeter to check serviceability a low resistance indicates

forward bias

When using an ohmmeter to check serviceability a high resistance indicates

reverse bias

When using the diode function to check serviceability a what indicates forward bias

a voltage reading similar to the barrier potential

When using the diode function to check serviceability a what indicates reverse bias

a reading of OL

Zener diode bias

reverse bias

Zener diode used for

regulating voltage

Varactor/varicap diode bias

reverse bias

When voltage is increased through a varactor/varicap diode the capacitance of the diode

decreases

Photodiode converts

light energy to electrical energy

LED stands for

light emitting diode

LED converts

electrical energy to light energy

LED bias

forward bias

Colour of the light emitted depends on

band gap energy (material of LED)

What is required for a series LED circuit

a series resistor

What is the nominal voltage drop for a LED in a DC circuit

2V

Seven-segment LED display

uses LED segments or bars that can be lit in combinations to form any number 0-9

In forward bias the depletion region

narrows

In reverse bias the depletion region

widens