Transcript Transistors - BDJ Engineering

START
Daily Sprint
1.What is a capacitor? Draw its symbol.
2.Draw a circuit diagram for a camera
flash.
3.What else could a capacitor be used
for?
MSA Prep
Solve:
x=4
y=2
3x +4y +x2 - xy
Conclusion Questions
1.
-
Describe something other than the
examples you’ve been given that you
believe uses a capacitor and its
function in the device.
Conclusion Questions
2.
What do capacitors have to do with
the dangers of older television sets?
- Older TV’s used large capacitors to operate.
Those capacitors held enough charge to
seriously injure someone if they touched it. The
charge will remain in those capacitors long after
the TV is out of use.
Transistors
Transistors
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Transistors
Parts of the Transistor
The First Transistor
Transistors as Amplifiers
Transistors as Switches
Night Light Circuit
This presentation is intended to be used with Activity 6.2.6 Transistors
Transistors
Transistor: A small electronic device used in
a circuit as an amplifier or switch.
Symbol for Circuit
Diagrams
Parts of the Transistor
EMITTER
BASE
COLLECTOR
The small base current controls
the larger collector current.
The First Transistor
•Considered by some to be the
greatest invention of the 20th
century
•Invented at Bell Laboratories
in 1947
•It is a crucial component in
almost all modern electronic
devices
•Engineers are working toward
making them smaller so that
more can be placed on
computer chips. Many today
are already smaller than a
human hair.
Replica
Transistors as Amplifiers
Small load
(input)
Large load
(output)
Transistors as Switches
Build the circuit as shown.
DC
1K
When the switch is closed, you
should notice that the LED in the
circuit connected to the base is very
dim.
But the other LED that is controlled
is much brighter.
A small current amount switching
on a larger current
Small Current
Load
5.1 K
Large
Current
Load
Night Light Circuit
Challenge: Create a system with a light that comes on
when it is dark, similar to a street light.
In the following circuit, will the LED be bright at day or night?
The LED will be bright during the day
because brightness causes the
photoresistor’s resistance to
decrease.
When the resistance of the circuit
decreases, more current can flow to
the LED.
Night Light Circuit
In your engineering notebook, sketch the circuit shown below.
Current will always take the path of
least resistance.
Use a highlighter to trace the path
that current will take from the
source.
Does current reach the base of the
transistor?
Will current be able to reach the
light?
Night Light Circuit
In your engineering notebook, sketch the circuit shown below.
In brightness the photoresistor’s
resistance is low.
Use a highlighter to trace the path
when there is very little resistance
from the photoresistor.
Does voltage reach the base of the
transistor?
Will voltage be able to reach the
light?
Night Light Circuit
In your engineering notebook, sketch the circuit shown below.
In darkness the photoresistor’s
resistance is high.
Use a highlighter to trace the path
when there is a large amount of
resistance from the photoresistor.
Trace the secondary path of
resistance.
Is the voltage high enough to
activate the base circuit of the
transistor?
Will current be able to reach the
light?
Night Light Circuit
Build the circuit as shown to test using actual components using Snap Circuits®
spring sockets.
If the circuit does not work as expected, troubleshoot using the
flow chart provided in Activity 6.2.6 Transistors (omit the
suggestion to check solder connections).
Image Resources
Microsoft, Inc. (2009). Clip Art. Retrieved January 27, 2009, from
http://office.microsoft.com/en-us/clipart/default.aspx