Tech Square

Posted by Drew Eckhardt (A) on August 29, 2007 at 19:14:10

In Reply to: RE: Question - any help appreciated posted by hukkfinn on August 26, 2007 at 08:39:04

9VAC actually varies between -12.7V and +12.7V.

Devices could depend on this by using a pair of half-wave rectifiers to produce a bipolar supply at something beyond +/- 9VDC; perhaps +/- 11V (depending on capacitor size and load) which gives enough headroom to use 3-terminal regulators for a solid supply. Most op-amps and push-pull audio circuits require split +/- supplies, and most devices get there with separate recitifers + filters instead of a virtual ground device.

9VDC could be AC with a half or full-wave rectifire producing a wave form with no negative component to produce the negative power supply; or a filtered 9VDC with no headroom for regulators.

You want to use a real 9VAC supply.

Edits: 08/29/07