| ??? 08/15/05 12:42 Read: times |
#99418 - Answer Responding to: ???'s previous message |
James said:
I know the formula to calculate a low pass filter and given C=100nf how would I calculate the value of R given your proposed circuit if I wished my cutoff frequency to be 15khz.
Because there are other resistors in series with the input I am not sure which resistors would figure in the calculations. I would think only one of the 5.1k resistors would need to be figured into the equation. The filter is meant to eliminate fast spikes and HF-noise being superimposed on Vcc = 3V. So, look at the components being connected to Vcc = 3V. Now, cut this connection, insert a 100Ohm resistor and connect a 100nF capacitor from this connection point to ground. Corner frequency of this low pass filter is fc = 1 / (2 x pi x R x C) = 15.9kHz Kai |
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