Microsoft Word - Digital Logic Design v_4_6a

 Different Switches
Instead of mechanical switches, we can also use electronic switches:

 A normally open (n.o.) switch is closed when pressed.

 A normally close (n.c.) switch is open when pressed

 Example of setting up a LED and a switch

U

A

B

21 3 F

GND

GND

R

R

F=1  LED on

F=0  LED off

Vcc

Switch open  F=1

Switch closed  F=0

Note: Typically R=1 k Ω is used.

N

-

V

+

When Current Flows the

Relay opens

Spring

contact

Relay as n.c.

Gate

Source

Drain

Base

Emitter

Collector

PMOS FET as n.c.

Négative Channel Métal

Oxide Semiconductor

Field Effect Transistor

PNP BJT as n.c.

Bipolar Junction

Transistors

N

-

V

+

When Current Flows the Relay

closes

Spring

contact

Relay as n.o.

NMOS FET as n.o.

Positive Channel Metal Oxide

Semiconductor

Field Effect Transistor

NPN BJT as n.o.

Bipolar Junction Transistors

Gate

Drain

Source

Base

Collector

Emitter