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!
no, the supply powers only the loop.The VCO has another (clean) supply.
But the noise is there without any load, and is gone as soon as I remove the 4700uF cap (with 2,2 Ohms resistor).
In a REF03 datasheet I remember a workaround for capacitive loads (with booster transistor) by putting a cap across the regulator.
The sideband noise graph was where I first Noticed the problem-the noise obviously modulates the VCO via the control voltage (from the loop).
I want to understand the problem.The setup is not so uncommon.
But of course,if there is a low noise 10V /150mA LDO that can deal wich capacitive load (preferably a leaded version), I am also open for any suggestion.
Gesendet: Mittwoch, 31. Mai 2017 09:33
An: Angst Günther
Antwort an: firstname.lastname@example.org
Betreff: Re: - Re: Noise problem with a REF01 with booster transistor
Re: Noise problem with a REF01 with booster transistor
reply from iamPhil<FormerMember> in Power Management - View the full discussion<https://ez.analog.com/message/303829?commentID=303829&et=watches.email.thread#comment-303829>