walid Posted April 25, 2010 Report Share Posted April 25, 2010 Hifor the LPF shown below, the cuoff frequency is at -3dB or -6dB and why?thanks Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 26, 2010 Report Share Posted April 26, 2010 The 4.7nF capacitor creates a lowpass filter with the unknown value of the source resistance. The 10k resistor and 6.8nF capacitor create another lowpass filter.If the cutoff frequency of both filters is the same then their total is -6dB because each filter is -3dB. Quote Link to comment Share on other sites More sharing options...
walid Posted May 31, 2010 Author Report Share Posted May 31, 2010 The 4.7nF capacitor creates a lowpass filter with the unknown value of the source resistance. The 10k resistor and 6.8nF capacitor create another lowpass filter.If the cutoff frequency of both filters is the same then their total is -6dB because each filter is -3dB.If the cutoff frequency of both filters is not the same? is it sitll -6dBthanks Quote Link to comment Share on other sites More sharing options...
audioguru Posted June 1, 2010 Report Share Posted June 1, 2010 If the cutoff frequency of both filters is not the same is it sitll -6dB?No.You need to calculate the amount of attenuation. One filter might pass the cutoff frequency of the other filter then the attenuation is only -3dB. Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted June 2, 2010 Report Share Posted June 2, 2010 Phase shift oscillators produce 180 degrees phase shift using cascaded RC stages. Maybe the components are chosen so that each stage is independent of the other and reduces the loading effect, which would keep the phase shift at 90 degrees at best. Quote Link to comment Share on other sites More sharing options...
ARUN CHOWDARY Posted October 24, 2010 Report Share Posted October 24, 2010 please indicate the polarities of the capacitors Quote Link to comment Share on other sites More sharing options...
Hero999 Posted October 24, 2010 Report Share Posted October 24, 2010 please indicate the polarities of the capacitorsWhy? 4.7nF and 6.8nF capacitors will be non-polarised anyway so that's a silly question. Quote Link to comment Share on other sites More sharing options...
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