The NPN transistor as a circuit element

heartlustElectronics - Devices

Nov 2, 2013 (3 years and 7 months ago)

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The NPN transistor as a circuit element

Collector

Base

Emitter

“Tin Can”

Transistors

Replace Mechanical Switches

NPN
-
Transistor

The 1960’s transistor

Collector
OR

Drain

Base
OR
Gate

Emitter
OR

Source

The “Tin Can”

NPN
-
Transistor

Transistors are constructed differently and this fact is reflected in the names that are
given to the pins. As a first pass at this technology, it will not hurt to associate the
names in pairs.

However, ultimately the
operational principles for the
pins with similar names is not
the same for different types of
transistors.

it isn’t tin and
it isn’t a can!

Emitter

Silicon structure with extra
electrons in its structure

Silicon structure with
extra electrons in its
structure

Silicon structure with a shortage
of electrons in its structure

n
-
type material

p
-
type material

Bipolar Junction Transistor

NPN
-
Transistor

n

p

n

Emitter

negative

terminal

positive

terminal

If this switch is
closed, the light
will turn on if
the switch in
the base circuit
is closed.

Ground
connection

Ground
connection

Ground
connection

Simple Switching Circuit Example

NPN
-
Transistor

Bipolar Junction Transistor

This switch now controls the light.
If it is closed, the light will go on.

n

p

n

Emitter

negative

terminal

positive

terminal

electron flow

Ground
connection

Ground connection

Ground connection

Simple Switching Circuit Example

NPN
-
Transistor

Bipolar Junction Transistor

Emitter

negative

terminal

positive

terminal

Ground connection

Ground connection

Ground connection

NPN
-
Transistor

Another view of the npn transistor switch circuit

Emitter

negative

terminal

positive

terminal

Ground
connection

Ground connection

Ground
connection

This new cartoon is a little closer to
reality since it includes a drawing of a
real npn transistor with its correct pin
locations.

Ground connection

Negative
terminal

positive

terminal

Ground
connection

NPN
-
Transistor

NTE 198

Notice that the
base connection is
not in the middle
of the device
package even
though inside the
package the base
is in the middle of
the device.

NTE 198

Negative terminal

positive

terminal

Ground
connection

Emitter

Base

Collector

NPN
-
Transistor

Negative terminal

positive

terminal

Ground
connection

Emitter

Base

Collector

NPN
-
Transistor

Negative terminal

positive

terminal

Ground
connection

Emitter

Base

Collector