Negative power supply

[electronicslearner77]

Suppose my circuit require -12v. If I have a 12v supply, is it ok that I connect the negative of the supply to the circuit? basically what is the difference between actually connecting the negative source and connecting the positive supply but interchanging the terminals.

 

[BradtheRad]

As a general rule what you describe is correct, as long as we're talking about just one power supply, and no more.

However if you introduce a second supply (or a second ground connection), then you must think through everything you're doing, as to proper polarity, etc.

 

[AMS012]

If the power supply says it is 12v, it means that the positive terminal is at 12v higher potential than the negative terminal. Everything is relative. You can connect the negative terminal to the circuit to get -12v. Remember, -12v is with respect to the node the positive terminal is connected to.