Easy question from a newbie - Electronic Circuits Projects Diagrams Free

galneweinhaw · 29th April 2004, 06:24 PM

Hi,

I am trying to build a circuit w/ a TL072 IC. It requires a +, - and ground.

If I want to put my little circuit in a box how do I get this +/-/gnd without a big seperate power supply?

The way I know of is 4 9V batteries (+18V/-18V/gnd).... a bit cumbersome.

Is there an easy way to get +/-/gnd from an off the shelf plug in transformer?

Thanks, any help is greatly appreciated.

PS: this forum looks sweet, I can wait to get a chance to browse around a little more, esp. the projects.

**Nigel Goodwin** · 29th April 2004, 06:41 PM

Why do you need +/-18V? - if you use +/-9V you could use two 9V batteries. Using batteries or a mains PSU depends greatly on what the circuit does and what it's going to be used for (and where). Using batteries has the huge advantage that it's portable - and as long as current requirements are low the batteries can last a good long time.

Crofty · 4th May 2004, 06:49 PM

The usual trick is to use an Op Amp, biased to half supply, with a decent electrolytic cap on the output. This then outputs your Gnd, then use the main supply as your +/-

Steve

galneweinhaw · 4th May 2004, 07:23 PM

Quote:

Originally Posted by Crofty

The usual trick is to use an Op Amp, biased to half supply, with a decent electrolytic cap on the output. This then outputs your Gnd, then use the main supply as your +/-

Steve

Can you direct me toward an example schematic please?

Crofty · 5th May 2004, 11:02 AM

I've done a diagram, which I've zipped, as I can't upload in PDF format.

Its a straight forward OPA divider, with decent rail smoothing. If you need higher current? the same method can be applied to more powerfull OPA's ie: LM380 etc.

Note: Input can be upto the max volts for the OPA, 30 Volts off the top of my head. Make sure the 2 x 470uF's are rated for what every voltage you end up running on..

Hope this helps

Steve

grrr_arrghh · 5th May 2004, 05:20 PM

take a quick look at http://www.electro-tech-online.com/viewtopic.php?t=8755

amongst all the misunderstanding, there is some real information in there!

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29th April 2004, 06:24 PM	(permalink)
galneweinhaw	Easy question from a newbie Hi, I am trying to build a circuit w/ a TL072 IC. It requires a +, - and ground. If I want to put my little circuit in a box how do I get this +/-/gnd without a big seperate power supply? The way I know of is 4 9V batteries (+18V/-18V/gnd).... a bit cumbersome. Is there an easy way to get +/-/gnd from an off the shelf plug in transformer? Thanks, any help is greatly appreciated. PS: this forum looks sweet, I can wait to get a chance to browse around a little more, esp. the projects.

29th April 2004, 06:41 PM	(permalink)
Nigel Goodwin	Why do you need +/-18V? - if you use +/-9V you could use two 9V batteries. Using batteries or a mains PSU depends greatly on what the circuit does and what it's going to be used for (and where). Using batteries has the huge advantage that it's portable - and as long as current requirements are low the batteries can last a good long time. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

4th May 2004, 06:49 PM	(permalink)
Crofty	The usual trick is to use an Op Amp, biased to half supply, with a decent electrolytic cap on the output. This then outputs your Gnd, then use the main supply as your +/- Steve

5th May 2004, 05:20 PM	(permalink)
grrr_arrghh	take a quick look at http://www.electro-tech-online.com/viewtopic.php?t=8755 amongst all the misunderstanding, there is some real information in there!