Experiment 5: BJT Switch
Experiment 5
BJT Switch
OVERVIEW
A Bipolar Junction Transistor circuit can be designed to operate either at cut-off or at saturation,
to form the so called ‘Switch’. This switch can be used to drive different components like LEDs,
low-voltage fans, etc.
In this experiment, you will connect and test a transistor switch that will switch an LED, ON or
OFF.
EQUIPMENT
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Transistor: 2N3904
Power Supply: 5 V
LED
Digital Multimeter
Resistor: 100 Ω, 1 kΩ
PROCEDURE
1. Connect the circuit shown in Figure 6-1.
Figure 6-1
2. Switch the input voltage to 0 V using the switch at the base of the transistor. Observe the
state of the LED.
3. Measure and record the base current 𝐼𝐵, collector current 𝐼𝐶 and the collector-emitter
voltage 𝑉𝐶𝐸 .
4. Switch the input voltage to 5 V using the switch at the base of the transistor. Observe the
state of the LED.
5. Measure and record the base current 𝐼𝐵, collector current 𝐼𝐶 and the collector-emitter
voltage 𝑉𝐶𝐸 .
6. Verify that the BJT is saturated using the equation 𝐼𝐵
𝐼
>𝛽𝐶 .
Note: You will have to acquire 𝛽𝑚𝑖𝑛 from the datasheet of the BJT.
𝑚𝑖𝑛
7. Simulate this experiment on MultiSim to verify your results.
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