| Electronics > Beginners |
| LPF question |
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| stoica adrian:
Hello, I have two qestions, if you can help me. What happens after you pass the 3db point of a LPF, and witch is the maximum ° that you can obtain with a LPF? |
| Bassman59:
--- Quote from: stoica adrian on July 13, 2018, 03:00:38 am ---Hello, I have two qestions, if you can help me. What happens after you pass the 3db point of a LPF, --- End quote --- Pass it from which side? To the right (increasing frequency) of the 3 dB point, the response increases towards unity, at which point it flattens out. To the left of the 3 dB point, the response decreases with a slope given by the number of poles in (the order of) the filter. One pole, your attenuation goes as 6 dB/octave. Two poles give an attenuation of 12 dB/octave, and so forth. --- Quote ---and witch is the maximum ° that you can obtain with a LPF? --- End quote --- That too depends on the order of the filter. |
| Circlotron:
RC low pass filter output would approach 90 deg phase lag, I expect. Probably never quite get there. |
| David Hess:
90 degrees maximum per pole or order. |
| Audioguru:
A single R and a single C makes a very poor filter. it rolls off at only 6dB (half the level) for each octave (10 times the frequency). Use an opamp or a few to make a multi-order active filter. |
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