Transcript Slide 1
Foundations of Technology NPN Teacher Resource Unit 4 Lesson 4 © 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning™ Foundations of Technology Objective: You will build a simple circuit to show that a NegativePositive-Negative (NPN) transistor will serve as a current amplifier. Collector NPN Base 2N3904 Emitter The flat side faces up You will need the following parts from your kit: 1. 2. 3. 4. 5. 6. 7. 8. 9. Breadboard 220 ohms resistor (red, red, brown, gold) 3300 ohms resistor (orange, orange, red, gold) NPN Transistor 2 @ LED (light emitting diode) 9 volt battery lead 3 wires 9 volt battery Pushbutton switch Use this schematic to construct the experiment. base 220 Ohm 3.3K Ohm + 9 volts - Quick Check: Your circuit should like this one. 1. 2. 3. 4. This circuit will light the LED’s. Electrons will not flow through the emitter collector until there is current through the emitter base combination. This makes a small current control a large current which is referred to as amplification. An increase of current through the emitter base will result in a larger current through the emitter collector side of the circuit. If you change the 3.3K Ohm resistor you will see a change in LED brightness. You can also measure this with your Amp meter. 1. 2. 3. 4. 5. Connect the 9 volt battery. Observe the brightness of the LED’s. Press the pushbutton switch. Observe and compare the brightness of the LED’s. Release the pushbutton, both LED’s should turn off. Troubleshooting: 1. If the LED’s do not light up, check to make sure they are in correctly. 2. Check the battery. Does it have voltage? 3. Are there any breaks in the circuit? 4. Is the NPN in the right way? By completing this experiment, you should have noticed the light from the LED on the emitter collector was brighter than the LED from the emitter base. The LED’s only light up after you press the button. In complete sentences, write what you learned about a NPN transistor in a circuit.