Powering opamp with 9v?

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Powering opamp with 9v?

Postby FrankKair » 20 Oct 2012, 10:26

Almost every circuit I have looked (if not all of them) have their opamps powered with 4.5v by a voltage divider.

Is there a problem by powering the opamp with 9v?
I mean, for higher thresholds feedback loop diodes (like an LED) it would be better to have 9v on the opamp right? To achieve more "signal boost" and then reaching the led clipping.

Am I right or this does not work?

Thanks in advance,
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Re: Powering opamp with 9v?

Postby induction » 11 Feb 2013, 21:31

This thread is a few months old, but in case you haven't gotten an answer elsewhere:

If you look at the schematics again, I think you'll find that usually the op-amps are indeed powered with 9V in most cases (9V attached to V++ pin and ground attached to V-- pin). The voltage divider you see is usually connected to the non-inverting input. This serves to center the signal between V++ and V-- for maximum headroom. Otherwise the op-amp would clip the negative half of the signal.

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Re: Powering opamp with 9v?

Postby Ice-9 » 11 Feb 2013, 23:05

You need to lookat the opamp datasheet, opamps use a bipolar power supply which in the case of most guitar pedals using a 9v battery this happens by a resistor voltage divider across the 9v supply giving 9v-4.5v- 0v this translates into +4.v - 0v and -4.5v where the Vbias is the 0v. Most opamps can easily work on a +/- 15v so if you already have a voltage divider in the circuit then it is possible to run higher voltages. One important point is to check that the voltage specs of the capacitors are high enough.
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