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Old 11th March 2009, 08:31 PM   #1
rhysh is offline rhysh  United Kingdom
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Default Looking for the ideal linear SMD voltage regulator, any suggestions?

Hi,

I am looking for a voltage regulator to power two low power standard dual opamps. I have dug around various websites and datasheets for hours, but i was also wondering if anyone here has anything to say.

I will need to regulate from +30v and -30v down to +15v and -15v. I need somthing in some kind of SMD package, with low noise etc. A fixed regulator would be ideal, but a adj regulator would be okay with me. I wont need more then 250ma of current per regulator.

Any suggestions?
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Old 12th March 2009, 02:07 AM   #2
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http://www.fairchildsemi.com/ds/KA/KA7915.pdf

auf Seite 15 ist ein Schema gezeichnet.

15V * 250mA sind 3.75W, das bedeuted gute Kühlung (Kühlkörper: 15K/W).

Das tut's für OPAMPS.

Falls ein Widerstand von 47 Ohm 5W vorgeschalted wird, plus 1000 uF zum Filtern, gibts garantiert keinen Rippel mehr und der Regler bleibt kalt, da der Widerstand fast alles Verheizt (bei 250mA).
Dazu filtert der RC oberhalb 3.2 Hz den Dreck weg und das Rauschen des Reglers kann niemand hören (PSRR von OPA).
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Old 12th March 2009, 02:07 AM   #3
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http://www.fairchildsemi.com/ds/KA/KA7915.pdf

page 15 contains schematics for such a supply.

15V * 250mA is 3.75W, this requires good kooling of 15K/W.

This works fine for OPAs.

If you take a resistor of 47 Ohm 5W in series between 30V and regulator together with 1000 uF (at regulator input) for filtering, no ripple will reach the regulator and the regulator stays cold, the power is dissipated at the resistor (at 250mA).
This filter gives lowpass at 3.2 Hz, keeps away all incoming noise in the audio bandwidth an noise of the regulator is not audible due to the PSRR of OPA.
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