On Wed, 11 Jul 2007 18:59:17 GMT, Joerg
wrote:

John Larkin wrote:
I need to make -12 from +12, at maybe 500 mA, and all the obvious
inverting switching regulators suck for one reason or another.

The LM5112 is a 50-cent fet gate driver.


50 cents is a lot of money in electronics ;-)

Not in my electronics!


How about the old CD40106? The BCX70K seems overkill as well but only by
a cent or so. I think you need to throw in another transistor or two
because you may need a current limit, unless a short isn't going to have
nasty consequences.

After due consideration, not to mention being yelled at by junior
staff members, it looks like we'll be going to a flyback with custom
magnetics. It was an interesting diversion, anyhow.


BTW, I'd probably be a bit squeamish about letting Vbe climb above -3V
on the BCX. But it's under abs max.

I tested some recently, and got around 5.1 typ Vbe breakdown. Beta
degradation wouldn't matter much in a common-base circuit like this!

I'm going to have to play with the blocking-oscillator converter one
of these days, just for fun.


John