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Explain me the operation of transistors

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Exodus

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hello my questions is on the operation of transistors i have a basic under standing of how they work meaning i know that you need to put a small voltage on the base to make the collector conduct to the emmiter but i am a beginning tinkerer i built a basic circuit with a transistor as a switch i had 5 volts connected to the collector only but when i took my reading on the base there was 5 volts there does the collector conduct to the base if there is no voltage on the base? i wish i could draw you a diagram of the circuit. anyway when i did put a 5 volt source on the base my led came on it should have turned off when there was a voltage applied because i had the emmiter connected directly to ground adn i was taking my output off of the collector below a resistor please help if you can.
 

truebs

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Re: transistors

please be clear ....and try providing the circuit diagram (from any schematic editor) for proper analysis.
 

DrWhoF

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Re: transistors

You can't connect collector directly to +5V. If you want to turn a LED on and off you should use a 2.2kΩ resisyor connected to collector then a LED connected between this resistor and +5V. Applying control voltage to transistor's base should be through a 4.7-10kΩ resistor.
Also to switch transistor off you should connect another 10-100kΩ resistor between its base and emitter.
For further tests try to use new transistor because I think this one is already dead.
DrWho
 

ARTMehr

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transistors

1) whitch kind of Transistor ? Si/Ge or NPN/PNP
2) When you want to use a Tr. as a switch, the voltage between Base and Emitter (NPN/Si) must be 0.7 Volts.
3) check the cook-book for your transistor details.
4) A simple Bias is as Dear DrWhoF !:idea:
 

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