Easy question from a newbie

[galneweinhaw]

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]

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]

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]

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]

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]

take a quick look at https://www.electro-tech-online.com/threads/help-question.8755/

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