Transistor Switching

Objectives

1. Familiarize ourselves with transistors by building a simple circuit that uses a transistor a switch and LED.
2. Find the Beta value for the 2N3904 transistor by setting up the circuit shown in the lab manual and graphing the current measurements.

Objective 1:

Values/items used in Diagram:

S1: switch

R1: 180 Ohm resistor

R2: 10 K Ohm resistor

R3: 680 Ohm resistor

Q1: 2N3904 transistor

D1: LED

Circuit Set Up/Diagram

Set up

Conclusion: the LED lights up when the make shift switch is connected, we have done something right.

Objective 2

Circuit set up:

When everything was set up we measured the current between the 10 K potentiometer and the base of the transistor as well as the current leaving the transistor.

Data Points

Using the measured values from the experiment we can graph the two currents to find our Beta value.

mA passing through A1		mA passing through A2
0.11		16.62
0.15		16.7
0.2		16.81
0.25		16.95
0.3		17.07
0.35		17.18
0.4		17.32

Excel graph of data points

By apply a best fit for our data we can conclude that the beta value for the 2N3904 transistor is approximately 2.43. The slope of the line is the Beta value we seek.

Conclusion:

This experiment demonstrates how transistors can be used to either switch the flow of the current or create a gain in current.