Transistors Lab

Introduction
         In this lab, we try to explore the characteristic of a 2N3904 transistor. In this experiment, we will analyze the beta value of the transistor. We will use a variable resistor box in order to change the current at the base. We should see a linear relationship of the current in the base and emitter until it reach the saturation level. When the transistor is saturated, there will be no more gain in the emitter even though the current of the base keep increasing.

Experimental


The circuit that will be built is going to follow the schematic below:

Schematic of the circuit but change the pot to a variable resistor

Building the circuit is as follow:

The setup of the resistor and voltage source connected in series

The setup of the breadboard for this experiment

 The data taken is as follow:

Base Current (mA)	Emitter Current (mA)	R(kΩ)
0.247	38.5	15.05
0.240	38.4	15.5
0.308	40.9	12
0.284	40.1	13
0.257	38.5	14
0.227	37.3	16
0.330	41.3	11
0.369	42.8	10
0.219	37.4	17

After making some measurements, it is decided that the transistor will saturate if we use 8kohm resistor.

After making some calculation the saturation occur when the base is around 0.5mA.

By looking at the graph, however, we can figure out the gain of the transistor since the beta value is actually the slope which is 37.0.


Conclusion


This lab shows us that the base and the emitter current has a linear relationship. In the graph that is obtained, the R^2 value shows our precision as it gets closer to one. The R^2 value that we have for this appears to be 0.983, which is close to one. Some discrepancy that contributes to the R^2 value not being one is that the resistor box is not exact when we change it. These values contributes to the error we got.