Part of Made in India,Design Innovation
Workshop,2015
A Fresh New Experience in Project-‐Making & Learning!
PHYSICS INVESTIGATORY PROJECT ON
TRANSISTOR AS AMPLIFIER & SWITCH
Do you know that there are billions of transistors used in the produc6on of ICs and microprocessors? Transistors are not only used for amplifica6on in sound systems but their ability to switch between the two states (ON/OFF) makes them the nerve cell of informa6on technology. In this project, you will learn about the characteris6cs of a transistor and how can it be used as an amplifier and a switch.
In this project, you will need a transistor, two resistors, a preset, two LEDs, a breadboard, a mul6meter and a few connec6ng wires. Varying input voltage is provided to the base-‐emiLer junc6on of the transistor using a voltage divider circuit made using a preset. The cut-‐off, ac6ve and satura6on regions of the transistor are iden6fied by comparing the intensity of the two LEDs, one on the input side (base-‐emiLer junc6on) and the other on the output side (collector-‐emiLer junc6on).
In the cut-‐off region, both the LEDs are OFF. In ac6ve region, the LED connected to the collector-‐emiLer side glows brighter than the LED connected to the base-‐emiLer side and on rota6ng the preset, the intensity of the former LED increases more than the laLer.
Now, an input voltage was set at the common terminal of the preset and it was measured using a mul6meter. The base and the collector voltages w.r.t the emiLer were measured and compared. Similarly, the base current (Ib) and collector current (Ic) were measured and compared, using which the amplifica6on factor (hFE = Ic/Ib) was calculated. The experimental value of hFE lies between 100 and 400 and therefore, it verifies that the transistor is in ac6ve region and acts as an amplifier with the base-‐emiLer junc6on forward biased and the base-‐collector junc6on reverse biased.
When the preset was rotated to its extreme leU, both the LEDs glow brightly and the transistor reaches its satura6on stage. The amplifica6on factor was calculated as above. The hFE obtained was less than 100. In this case, the transistor acts as a switch. Again the base and the collector voltages were measured and compared to verify the condi6on of the satura6on state. Both the base-‐emiLer and base-‐collector junc6ons are forward biased in the satura6on state. The value of the satura6on voltage for the transistor was found to be 0.25-‐0.6 V.
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You may also refer to the video: TransistorsFor more projects visit our website: CoolJunk
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