Timeline for Is -3dB bandwidth defined for any type of transfer function?
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jul 6, 2021 at 10:50 | comment | added | psmears | @user253751: That would be problematic, but arguably that's not really a filter (the question is tagged "filter"). | |
| Jul 6, 2021 at 9:31 | comment | added | Criticizing Israel not allowed | really, any? What about a transfer function that never drops down to -3dB? | |
| Jul 5, 2021 at 18:59 | comment | added | Bimpelrekkie | @Carl There are no strict rules. In this case it is common to ignore the peak so the -3 dB (relative to the flat passband) will be the bandwidth so -21 dB. But if you want to define it differently, be my guest, as long as you make it clear what your definition is. If you prefer to define the bandwidth as the -3 dB point relative to the peak than that is your choice. But it is not common to define it like that. | |
| Jul 5, 2021 at 18:46 | comment | added | Carl | Let's say I have a lowpass filter that is underdamped, such as \$H(s) = \frac{1}{s^2+s+8} \$. The frequency characteristic \$H(j\omega) \$ has a low frequent asymptote with -18dB gain and I suppose this is the passband. However, it also has a peak at the resonant frequency (\$\sqrt{8} = 2.8 \$) and at this point the gain is -9dB. So where would you locate the -3dB point? At -21dB? At -12dB? | |
| Jul 5, 2021 at 16:34 | comment | added | Bimpelrekkie | @Carl Relative to Vin at DC? No relative to what you consider to be the passband. dB only defines one value being relative to another value. Can you find the -3dB point the same way for a lowpass filter and a bandpass filter? Yes, as stated: ...the point: the signal power at the output has dropped by a factor of 2 (compared to the passband). | |
| Jul 5, 2021 at 16:18 | comment | added | Carl | "-3dB means that the amplitude of the voltage has dropped by a factor of \$ \sqrt{2}\$" relative to what? Relative to \$V_{in} \$ at DC? Relative to \$V_{o,max} \$? Can you find the -3dB point the same way for a lowpass filter and a bandpass filter? | |
| Jul 5, 2021 at 14:52 | history | edited | Bimpelrekkie | CC BY-SA 4.0 |
added 86 characters in body
|
| Jul 5, 2021 at 14:44 | history | answered | Bimpelrekkie | CC BY-SA 4.0 |