I have some trouble measuring the cutoff frequency, of a simple lowpass fitler with the .MEAS command.

the command that I’ve used - .MEAS fc FIND frequency WHEN mag(V(out))=-3, this just returns nan values.

Br.

Marc H. Munkstrup

I have some trouble measuring the cutoff frequency, of a simple lowpass fitler with the .MEAS command.

the command that I’ve used - .MEAS fc FIND frequency WHEN mag(V(out))=-3, this just returns nan values.

Br.

Marc H. Munkstrup

mag(V(out))>=0 it is error.

I expect you want to find -3dB, and you are missing db() function. You was to find |V(out)|=-3, not in dB, but in linear magnitude, -3dB with linear magnitude is `mag(V(out))=0.707`

or use this instead :

`.MEAS fc FIND frequency WHEN db(mag(V(out)))=-3`

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Ahh of course, its not even possible for it to be -3 dB when it is the linear magnitude.

Thank you for clearifying

//Marc