That's correct - obviously, the negative regulator requires a transistor in the "opposite" sense - ie: NPN. Can't see the reason for having the 1 Amp fuse on the output of the regulator, however, because if the fuse blew, the output would rise to the unregulated input voltage, which could result in the destruction of whatever you're powering.... If you're concerned about overvoltage, you should employ a "crowbar" circuit - look it up on the 'net - which will blow the supply fuse before anything dramatic happens to the gear attached to the output. You can use a single 2N2955 and a single 2N3055 for the series pass transistors - at 3 Amps, they'll be coasting if they're on a reasonable heatsink. These devices are cheap, but the cases are NOT isolated - you'll need heatsink isolation kits for them. The only real "gotcha" is that the pinouts of the 7815 and 7915 are different! Chris ----- Original Message ----- From: "A.J. Tufgar" To: Sent: Thursday, November 28, 2002 5:43 PM Subject: Re: [EE]: 15, -15V @~3A PSU. > Allright I think this is my plan, I'm going to modify the supply here > from an LM7812 to LM7815 and only use one transistor. > http://www.mitedu.freeserve.co.uk/Circuits/Power/1230psu.htm > > I'm going to use a VCT trans as suggested and hook up another circuit > in the same configuration (with some obviuous modifications i.e. > 7915)to the neg terminal of the rectifier. > > For the negative side though I assume I use an NPN pass trans. instead. > Is this okay any 'gotchas' on doing this? Just want to make sure I > hook the negative pass transistor up correctly. > > Thanks for all your help, > Aaron > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads