Diodes and LEDs

Discussion D8.1

Kerns & Irwin

Sections 10-1 -- 10-5, 10-10

http://electronics.howstuffworks.com/diode1.htm

Covalent bonds -- Insulator

Semiconductors

Adding a very small amount of P or As to Si makes an n-type semi-conductor with an extra electron

Adding a very small amount of B or Ga to Si makes a p-type semi-conductor with a missing electron (a hole)

Diodes

http://www.mtmi.vu.lt/pfk/funkc_dariniai/diod/index.html

+ -

Light Emmitting DiodeLED

+ -

h

http://electronics.howstuffworks.com/led1.htm

Turning on an LED

+5VR LED

PLD output pin

+5VR LED

PLD output pin

1

0

+5V

+0.2V+1.7V

No current

Currentlight

no light

R =voltagecurrent

=5 1.7

15 x 10 -3 = 220 ohms

Turning on an LED

This is whatwe use in Lab

CPLD output pin0 V R

No Current

LED

no light

CPLD output pin+3.2 V R

Current

LED

light

R = voltage = 3.2 - 1.9 = 325 ohms current 4 x 10^-3

+1.9 V 0 V

0 V

0

1

R = 330 ohms