Kevin Weddle 2 Report post 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 Share this post Link to post Share on other sites
indulis 0 Report post Posted October 22, 2010 Do the math and plot the transfer funtion, then you will know (and should understand) what it does. Quote Share this post Link to post Share on other sites
Kevin Weddle 2 Report post 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 Share this post Link to post Share on other sites
audioguru 35 Report post 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 Share this post Link to post Share on other sites
Hero999 5 Report post 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 Share this post Link to post Share on other sites
