+18v and -9v in a JRC4558? Is posible?

Yoshi · March 25, 2022, 10:38:04 AM

hello, I´ve a simple (and maybe dum) question

Can I supply, in a JRC4558 Op-Amp, with +18v in Pin 8 and -9v in pin 4? This to create a 36v op amp?

Thanks

vigilante397 · March 25, 2022, 11:04:30 AM

You absolutely can, that's how Klon does it. You can still do a voltage divider on the 9V input for a +4.5V vref, which is brilliant as it's still right in the middle of +18V and -9V.

Yoshi · March 25, 2022, 11:30:48 AM

Yeah!!!.... But what happen is I use +18v and -18v ... the vref needs to be +9v?

r080 · March 25, 2022, 11:53:06 AM

In that case, your VRef is just "ground". If you are going there, you can search for circuits with bipolar supplies to give you ideas.

antonis · March 25, 2022, 01:38:01 PM

Quote from: Yoshi on March 25, 2022, 11:30:48 AM
But what happen is I use +18v and -18v ...

You have a very hot IC..

idy · March 25, 2022, 02:14:18 PM

It is only rated to +-15v. Magic smoke.

ElectricDruid · March 25, 2022, 03:45:21 PM

Quote from: idy on March 25, 2022, 02:14:18 PM
It is only rated to +-15v. Magic smoke.

Depends on the *exact* chip. There are some 4558's that are rated at +/-18V as the absolute max (which is equivalent to saying that +/-15V is the largest sensible supply voltage) and there are some that say +/-22V, which would make +/-18V possible.

You'd have to find a datasheet for the exact/particular version of the 4558 that you're using and make sure. Honestly though, I'm not sure I'd bother pushing it that close to the limits. What's wrong with a reliable +/-15V, which pretty much every op-amp in history was designed for?! And if +18V/-9V is the best way to get close to that, then perhaps that's the best way.

HTH

PRR · March 25, 2022, 11:14:16 PM

All those older chips are rated 36V, or +/-18V. They really prefer you use +/-15V which was once a real popular thing.

> +18v in Pin 8 and -9v in pin 4? This to create a 36v op amp?

Counting fingers and toes on me and the dog, that seems to be 27V, not 36V.

antonis · March 26, 2022, 08:26:22 AM

Quote from: PRR on March 25, 2022, 11:14:16 PM
Counting fingers and toes on me and the dog, that seems to be 27V, not 36V.

I feel sorry for your amputee dog, Paul..

duck_arse · March 26, 2022, 09:27:33 AM

Quote from: antonis on March 26, 2022, 08:26:22 AM
Quote from: PRR on March 25, 2022, 11:14:16 PM
Counting fingers and toes on me and the dog, that seems to be 27V, not 36V.

I feel sorry for your amputee dog, Paul..

my dog has no nose.

antonis · March 26, 2022, 09:31:00 AM

Quote from: duck_arse on March 26, 2022, 09:27:33 AM
my dog has no nose.

Either Mick Jagger has..

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+18v and -9v in a JRC4558? Is posible?