Transistor Switching Experiment

For this experiment we studied the behavior of a transistor. A good analogy for a transistor would be a faucet; in this case current is distributed from an emitter, and passes through a base that regulates the flow of current ending up in a collector.

First we set up the following circuit:

 

The switch for this circuit is modeled as a pair of wires that when they interact acts as an ON switch.

When doing this, the LED gets lit lightly.

The second part of this lab is to create a circuit where a finger tip will serve as a switch, there fore conducting current to the base of the transistor.

Two cables make contact with the finger tip skin and allow the flow of current.What the base of the transistor is doing here is amplifying changes in current coming from the skin.

For the final circuit layout, we constructed a circuit similar to the ones above. However, this time we put in a potentiometer that allowed us to regulate the flow of current throughout the transistor. The current from the base and the current going to the collector must be measured using ammeters.

R2 and R4 were removed from the original layout for the purpose of ease of measurement

The following currents were obtained:

Miliamps through A1	Miliamps through A2
0.25	44.3
0.30	47.2
0.35	50
0.40	52.5
0.45	54.5
0.55	58.3
0.60	60.5
0.65	61.7
0.70	63.2
0.75	64.65

If we take the ratio of the current going out of the emitter (A2) with respect to the current going to the base (A1), we could get BETA:

177.2
157.3333
142.8571
131.25
121.1111
106
100.8333
94.92308
90.28571
86.2

The average value for Beta would be 120.8

Graphical Representation of A1 vs A2