# positive and negative 12 V dc from a +12V dc signal?

Discussion in 'Electronic Basics' started by davidd31415, Jun 10, 2005.

1. ### davidd31415Guest

I'm looking for methods to obtain positive and negative 12 volt signals
from a single positive 12 v signal (simultaneously, not simply
reversing the polarity).

I'm specifically looking for a circuit design and an explanation of how
the circuit works.

Thanks,

Dave

3. ### Terry PinnellGuest

Another possibility is that Dave means 'supply', not 'signal'.

4. ### Bob MonsenGuest

Since you already have +12V, you really just need to get -12V. A smps
chip, along with a bit of supporting circuitry, can do that rather
easily; the idea is to, first allow, and then to stop current through an
inductor. When you suddenly stop the current feeding the inductor, the
magnetic field created by the current induces current to continue to
flow. This generates a big negative voltage spike, which, if captured
using a diode, can be used to create a -12V supply rail. Feedback
controls the oscillator which is alternatly starting and stopping the
current, and thus the output is regulated.

However, rather than have me describe it to you, look at the linear site
for inverting regulators here:

http://tinyurl.com/933to