Kevin Weddle Posted October 21, 2010 Report Share Posted October 21, 2010 LC filters have good attenuation at low frequencies and are less suitable at higher frequencies. 40db/decade is the attenution. Is -3db the nominal attenuation for unwanted frequencies? Should the final attenuation be more or less than -3db in order to be finished with filtering. Quote Link to comment Share on other sites More sharing options...
indulis Posted October 22, 2010 Report Share Posted October 22, 2010 Do the math and plot the transfer funtion, then you will know (and should understand) what it does. Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted October 25, 2010 Author Report Share Posted October 25, 2010 For example, a passband amplifer can have as little as 20db/decade roll-off. A cascaded passband amplifier can have a much higher roll-off. I normally see many filters in a circuit, is it to achieve an exact amount of filtering? I have 120Hz 10mVpp ripple coming from my 7805 voltage regulator, should I filter it out? Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 25, 2010 Report Share Posted October 25, 2010 I have 120Hz 10mVpp ripple coming from my 7805 voltage regulator, should I filter it out?10mV p-p is very small. If you want less ripple then increase the value of your main filter capacitor. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted October 26, 2010 Report Share Posted October 26, 2010 I have 120Hz 10mVpp ripple coming from my 7805 voltage regulator, should I filter it out?No, there's no need to filter out just 10mV of ripple. Quote Link to comment Share on other sites More sharing options...
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