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Basic Electricity 012-04367E

Exp 9- Diodes

Analysis

JJJJJJJJJJJJ

OOOOOO

OO OO

0.001

0.002

0.003

0.004

0.005

0.006

0.007

-3 -2 -1 0 1 2 3

Current

Diode Voltage

4007

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

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.

ÇÇ

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Collector Current (mA)

Base Current (mA)

10 Ohm load

47 Ohm load

100 Ohm load

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.