transistor as power switch

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Hi all .....

how to use a transistor switching circuit if the load is a positive voltage of the IC ...
I want to add the switching circuit on the microcontroller to control the IC so that the IC can be used for specific conditions ..
I'm avoiding using the relay because I will be using a lot of relay if I want to control more than 10 IC for different conditions ..

anyone can share the circuit?!?!?
 
Use a PNP transistor to switch the positive voltage on by grounding the base through a resistor, to turn it off remove the ground from the base or connect it to the positive supply. (See examples)
 

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Yes the 2n3906 can take up to 40V and 200ma, or use a bigger transistor if you need more voltage or current.But the base current has to shut off to turn the transistor off, If you are trying to switch 12V and your control voltage is 0 to 5 V you would need to add a 8.2V zener diode in series with R2 to get Q1 to turn off.
 
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Make sure the switching transistor is saturated while ON.
Do this by getting the base current high enough to ensure that Ic/Ib <10.
If Ic is very variable then Ib must be chosen for the highest Ic and you must then check that the transistor is still able to operate properly when Ic is low, i.e. when Ic/Ib approaches 2
 
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