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URGENT!!!Reply fast!!!BC 547 switching? Answered

My school exhibition's tomorrow and I need to do something urgent.There's a 7 VDC supply which is converted to 5 VDC by a voltage regulator(both have a common negative terminal).I need a BC 547 to act as a switch and complete the circuit of a device connected to the 7 volt circuit when the 5 volts is used as a signal and sent to the transistor.To put it in another way-The device needs to run on 7 volts when a 5 volt signal is sent to the BC547.I've got about 4 hours of time before I go to sleep(actually forced to!)and the exhibition's tomorrow morning!!!

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steveastroukBest Answer (author)2013-01-18

What's the problem ? Just put the transistor emitter to common ground, feed the base from a 470 Ohm resistor and the 5V trigger.
Connect the load from +7 to the collector of the transistor.

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Adarsh_tronix (author)2013-01-18

Thank you friend!You know what?I'm just 15 years old and still gets confused with resistance?And I don't know very much about the internal functioning of these transistors.I am just learning with the help of experts like you.Now let me try this out quickly!

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