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Measurements >> RF Measurements >> how to reduce the 60 Hz power line ripples
https://designers-guide.org/forum/YaBB.pl?num=1258235381

Message started by LeonQQ on Nov 14^th, 2009, 1:49pm

Title: how to reduce the 60 Hz power line ripples
Post by LeonQQ on Nov 14^th, 2009, 1:49pm

Hi All,

I wonder how to reduce the 60 Hz power line ripples in real measurement?

I grounded the inputs of my amplifier, but the output shown on the oscilloscope had a big ripple (around 30 mVpp) mainly 60 Hz freq component. I probed a high-impedance node through a discrete buffer, the buffer output impedance is low (tens of ohms), the oscilloscope input impedance is 1 Mohm.

Through all corner simulations my PSRR is not bad at 60 Hz (> 80 dB), and usually op amp PSRR is better at low freq than higher freq.

I wonder where usually these 60 Hz ripples would coupled in, from the discrete buffer? I am not sure.

Thank you for the help.

Leon

Title: Re: how to reduce the 60 Hz power line ripples
Post by pancho_hideboo on Nov 14^th, 2009, 10:44pm

(1) Observe DC Power Supplier Output by Oscilloscope without connecting DUT.
Is there no 60Hz ripple ?

(2) Confirm AC Ground of DC Power Supplier and Oscilloscope.
How do you feed AC power to these equipments ?

(3) Turn off every lights in the room.

(4) Use battery instead of DC Power Supplier

Condition of AC power feeding and Ground including DUT is very suspicious.