12V and 3A fixed voltage

[badboy_6120]

Hi
I have a circuit that run with 12V(fixed) and need about 3 amp current
can anybody help me how can I invert 18V DC to 12V DC(fixed) with around 3 amp current
tank you

[Hymie]

Such a circuit would be fairly simple – consisting of a suitably rated transistor, a zener diode and a resistor. But since you need to ask – I would recommend something like this:-

http://www.ebay.co.uk...3&hash=item2a109af51e

Although the seller is recommending a 2A load, giving a margin on the maximum 3A load – in your application the unit will be dissipating around 18W which should be well within its continuous rating.

[badboy_6120]

thank you Hymie
you don't have any schematics?

[LCDMAN]

Google DC-DC convertor. Pre-built/pre-packaged circuits/devices exist to do exactly this.

[LCDMAN]

Like these;

http://www.store.word...ter_Module-236-1.html

[LCDMAN]

Try RS Components, Farnell, Rapid Electronics, Mouser - the usual suspects.

[ChuckFickens]

I'd go for a switching regulator, otherwise you'll be wasting a lot of power just turning it into heat.

http://www.analog.com...products/product.html

[LCDMAN]

Powertrends (now part of TI) do some nice switching regulators, but buying small qtys can be tricky.

http://focus.ti.com/a...lyId=64&contentType=4

[Hymie]

If I had the components to hand – I’d build the device; but otherwise I’d buy the £5.99 device and save the bother.