PASCO EM-8622 BASIC ELECTRICITY - Manual (Page 42)

Basic Electricity 012-04367E
38
Exp 9- Diodes
Analysis
J J J J J J J J J J J
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JJ J
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J J J J J J J J J J J J O O O O O O O O O O
O
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O O O O O 0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
-3 -2 -1 0 1 2 3
Current
Diode Voltage
J
4007
O LED
The diode acts as a one-way valve for electricity. Current
can flow in one direction, but not in the other.
Extensions
➀
A zener diode would be similar to the 4007, except
that there would be a breakdown point on the reverse
biasing, beyond which the current would flow. This
makes them useful for power regulation.
➁
) The LED opens up at a higher voltage than the 4007
(and it lights up).
Exp 10- Transistors
Analysis
➁
X
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X X X XX X X X X X X X X X
0
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0 0.05 0.1 0.15 0.2
Collector Current (mA)
Base Current (mA)
2N3904 Transistor
100 Ohm load
➂ The linear region does not include the origin, due to
the non-zero voltage that the junctions within the tran-
sistor require to turn on. (Similar to the effect in lab 9)
➃ Beyond the “saturation point”, the transistor is acting
like a short circuit. It offers no resistance to the cur-
rent; so beyond that point, there is no amplification.
The current is limited only by the battery and resistor.
➄
The current amplification of the transistor tested was
249. This value will vary from transistor to transistor;
it’s usually between 150 and 250 for the 2N3904 tran-
sistors supplied with the lab.
Discussion
➀ This graph shows the results of applying different val-
ues for R2. The amplification remains the same in
each linear region, but the size of that linear region
changes.
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Ц Ц
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Ц Ц Ц Ц Ц Ц Ц Ц ЦЦ ЦЦ Ц Ц Ц Ц Ц Ц Ц Ц Ц Ц Ц Ц Ц
б б б ббб б б б б б б б б б б б б б б б б б б
0
10
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0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Collector Current (mA)
Base Current (mA)
Ñ
10 Ohm load
Ç 47 Ohm load
Ö
100 Ohm load
á
560 Ohm load
2N3904 Transistor
various loads
➁
The gain and/or saturation characteristics of the tran-
sistor will vary, although the basic shape of the graph
will remain the same.