I'm looking for a good way to create a -5v supply from +12v without splitting the 12v with diodes. I need to keep the 12v gnd in tact. I've looked at rectifying the neg side of a square wave from a 555 timer but the current output is low. I need to drive the negative side of 2 op-amps in a unity gain configuration.

Suggestions?

 

What is your current requirement for the -5v supply?

More to the point, why don't you post your schematic, and give some details about the inputs you're getting, and what outputs you require?

 

Hello,

Here is a link to an application from MAXIM.
http://www.maxim-ic.com/cookbook/powersupply/pdfs/CB2.pdf
It makes - 5 Volts from the +12 Volt source.
This page comes from the power-supply cookbook that is also mentioned in the electronic resource part of this forum.
http://www.maxim-ic.com/cookbook/powersupply/

Greetings,
Bertus

 

Best way to create -5V rail from 12v supply

hi

i recommend to try LMC7660,
see also MC34063A

 

The x7660 gives extremely limited current output, less than the rectified 555-output scheme.
Bertus' first link shows a scheme capable of 2A @-5V.
The MC34063A datasheet from Texas Instruments shows a -5v 1.5A supply in the applications portion. That schematic could be adapted to a 555 solution if the 555 were driving an external transistor that sourced current to an appropriately sized inductor.