Low pass filter (RC) has cutoff frequency error

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Low pass filter (RC) has cutoff frequency error #793

Closed dxhowardjack closed 2 years ago

dxhowardjack commented 2 years ago

Hi,

I'm trying the cutoff frequency formula f=1/(2pi r * c) on the Low pass filter example circuit. And I found it seems have 10 times error on frequency parameter. (divide the frequency by 10 would be true value)

I'm new to Electronic Engineering, feel sorry if I am wrong. Thank you.

pfalstad commented 2 years ago

hi,

f = 1/(2pir*c) = 85.11 Hz

If I replace the sweep input with a AC source fixed at 85.11 Hz:

https://tinyurl.com/2o8duapx

I get a peak output of 3.536 V, which is .7072 * the peak voltage of the source. power is proportional to the square of the voltage so that's .7072^2 = 1/2 the peak power of the source, as expected.