Transistor Switching

The objective of the lab is to learn the secrets of transistors and to use them in action.

Procedure:
We first start with the following circuit model using a 2N3904 transistor.

For S1, we used two disconnected wires to act as a switch.

Once connected, the LED would light up because current is flowing into the base of the transistor, and allowing the emitter to release current from the collector.

In the second circuit tested, R2 was removed with finger measured to have 1 MΩ. The skin was very dry.

Before connecting with the finger.

After connecting with the finger.

The last circuit was tested using a potentiometer to change the current entering the base while data was connected using two ammeters. Two resistors connected in series are used to protect the transistor.

From measuring the base current at different points, we come out with this chart.

Analysis:
From graphing the data, the beta value = 80.
The transistor begins to saturate at around 0.75 mA.