Simple transistor circuit help...

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jester

Joined Feb 17, 2010
1
Okay I'm making a very simple transistor circuit. The problem I'm having is that the 5v control is separate from the 12v supply for the load (there two entirely separate sources with separate grounds). I need to be able to control and supply the transistor with two separate circuits.thanks in advance for help.
 

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ifixit

Joined Nov 20, 2008
650
Welcome,

Can you connect the grounds of the two supplies together?

If yes, do it.
If no, use an opto-isolator on the +5V source control to the base. That will maintain the circuit isolation. Google: 'opto-isolator' if required.

Good Luck
 

Audioguru

Joined Dec 20, 2007
11,249
The transistor is connected as an emitter follower. When the base is at +5.0V then the emitter and load are only +4.3V, not +12V.
 
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