Download Transistor Basics - Lakeland Regional High School

TRANSISTOR BASICS
Lakeland Regional High School
October 20, 2015
TRANSISTOR BASICS
1
WHAT CAN IT DO?
• Although transistors have many applications
for now we will be concerned with only a
couple of them
TRANSISTOR BASICS
2
MANY TYPES OF TRANSISTORS
• For this presentation we will focus on the
Bipolar transistor.
• They can be either an NPN or a PNP
depending on the way they are
manufactured
TRANSISTOR BASICS
3
NPN AND PNP
• The NPN type have an arrow at the
emitter pointing out
• This is in contrast to the PNP type that
has an emitter arrow pointing in
TRANSISTOR BASICS
4
Bipolar Transistors
NPN
TRANSISTOR BASICS
PNP
5
What do we get out of them?

For every 1 ma of current to the
base of the transistor, we usually get
10 to 100 times more thru the
collector and this feature is very
useful

In the electronics world this
translates to a small signal in to get
a big signal out
TRANSISTOR BASICS
6
WHERE DOES THIS ENERGY COME FROM?
• Even though we git a big signal out we do not
get something for nothing
• Bipolar transistors also require connection to
a DC source- this is where the energy comes
from
• This does not make them any less useful
TRANSISTOR BASICS
7
What will we do with them?
For our lab experiment we will set
up a simple circuit that controls
how much voltage appears at the
base of the transistor.
 We will do this by varying the
resistance and thus the voltage
 This will control the current to the
base which will control the voltage
thru the collector

TRANSISTOR BASICS
8
What will we do with them?
When we have appreciable collector
current we say that the transistor is
“on”
 We will measure the base current,
base voltage and the collector
current

TRANSISTOR BASICS
9
What will we do with them?
This will tell us a lot about what is
going on and demonstrate how the
transistor is useful
 Eventually the transistor will go
into “saturation” and we will see
that the collector current levels off
(or stops increasing)

TRANSISTOR BASICS
10
Resistance from base to ground
TRANSISTOR BASICS
Base Current Ib
Collector Current Ic
11