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Diodes are semiconductor devices that allow current to
flow in only one direction.
Diodes are composed
of a junction between a P-type semiconductor and
an N-type semiconductor. Most diodes are made of silicon.
Silicon diodes turn-on strongly when the p-side is made approximately
0.7V higher than the n-side. The expression relating current through a diode
to the voltage applied across a diode
is given by:
| |
(1) |
where
Id is the diode current.
Vd is the voltage from the p-side to the n-side.
Vt is called the thermal voltage which comes from basic physics
and is equal to 0.026V at room temperature.
IS is the saturation current which depends on the way the diode
is fabricated. IS can be obtained from data books from specific
diode manufacturers.
From equation (1.1), it is clear that when ,a large current can flow. However, when Vd < 0 a negligibly
small reverse saturation current will flow.
Diodes have many electronic applications. In this lab
we will demonstrate that the diode is a rectifier, and then show
how a rectifier can be used with a transformer to
construct a DC power supply from AC wall current.
You will then use the power supply you make to power op-amp
circuits.
ENEE306 Lab1 Electronics for Audio and Comm
unications
Next: Experiment: Simple Half-Wave Rectifier:
Up: Laboratory 1: Diodes and
Previous: introduction
Neil Goldsman
10/23/1998