Hello,
I am designing a dual linear power supply for my home made oscilloscope project. The circuit is designed with 2 stage ripple suppression, the 1st stage is capacitor multiplier, the second stage is LM317/LM337.
Both side 1st stage capacitor multipliers(Q5 and Q6) are working well and providing a <2mV(@50Hz) output ripple.
The +15V side is working well and the output ripple of LM317 is further reduced to <1mV.
The negative 15V side is designed to track voltage of +15V using an OpAmp(U10). Now the problem comes. I have noticed a 70mV(p-p) high frequency oscillation at around 10kHz. I first thought the oscillation is coming from Q5 and Q6 so I connected pin 4 and pin 7 of U10 to the output side of LM317/LM337. I got buffed the high frequency oscillation has jumped twice to 150mV(p-p).
Could anyone help me to understand why is this oscillation happening and how can I reduce it?
Thanks a bunch!
Circuit
http://forum.allaboutcircuits.com/attachment.php?attachmentid=33461&stc=1&d=1313982049
Ripple at +15V output
http://forum.allaboutcircuits.com/attachment.php?attachmentid=33462&stc=1&d=1313982049
Ripple at -15V output
http://forum.allaboutcircuits.com/attachment.php?attachmentid=33463&stc=1&d=1313982049
I am designing a dual linear power supply for my home made oscilloscope project. The circuit is designed with 2 stage ripple suppression, the 1st stage is capacitor multiplier, the second stage is LM317/LM337.
Both side 1st stage capacitor multipliers(Q5 and Q6) are working well and providing a <2mV(@50Hz) output ripple.
The +15V side is working well and the output ripple of LM317 is further reduced to <1mV.
The negative 15V side is designed to track voltage of +15V using an OpAmp(U10). Now the problem comes. I have noticed a 70mV(p-p) high frequency oscillation at around 10kHz. I first thought the oscillation is coming from Q5 and Q6 so I connected pin 4 and pin 7 of U10 to the output side of LM317/LM337. I got buffed the high frequency oscillation has jumped twice to 150mV(p-p).
Could anyone help me to understand why is this oscillation happening and how can I reduce it?
Thanks a bunch!
Circuit
http://forum.allaboutcircuits.com/attachment.php?attachmentid=33461&stc=1&d=1313982049
Ripple at +15V output
http://forum.allaboutcircuits.com/attachment.php?attachmentid=33462&stc=1&d=1313982049
Ripple at -15V output
http://forum.allaboutcircuits.com/attachment.php?attachmentid=33463&stc=1&d=1313982049
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