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Noise problem with a REF01 with booster transistor

Question asked by GA14 on May 29, 2017
Latest reply on Jun 12, 2017 by iamPhil

Hello all,

I have a noise problem at an oscillator starting at abt 100 kHz up to abt 1 MHz offset from the carrier (see picture).

I measured the spectrum of the power supply - and there is a remarkable noise increase around 500 kHz +/-.Problem located.

I realized the supply (10V/100 mA) with a REF01 and booster transistor 2N 2905A.To reduce noise further, I put an RC lowpass at the output (2,2Ohms, 4700 uF).

Looks as if the unit is very sensitive to capacitive loads. I need to increase the 2,2 Ohms resistor at the output of the REF01 to abt 10 Ohms to get rid of most of the noise.

Do you have any suggestion to deal with this problem without increasing the resistor? (Put a capacitor across the REF01?)

Maybe I should change to AD587 instead of REF01, or would there be the same problem?

Your suggestions are very welcome!

Best regards,

Guenther

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