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Passive Filters - Engineering

Q1:

The maximum output voltage of a certain low-pass filter is 15 V. The output voltage at the critical frequency is

A 0 V

B 15 V

C 10.60 V

D 21.21 V

ANS:C - 10.60 V

I think it is more intuitive to think of it in terms of dB.

Max voltage is 15V, convert this to dB.
15V = 20*log(15) = 23.52dB.

Voltage at the critical freq will be 3dB less than this max.
23.52dB - 3dB = 20.52dB.

Then convert back to voltage 20.52dB = 10.62V.