Question about input voltage and dbFS

[ljy4468]

Hi
I've a question about dbFS.
I know that it is dB scale relative to Fullscale.

So In FFT plot, fundamental bin is -3dB below 0dB,
then input is -3dBFS. isn't it??

And I have a question.
If input Vfs=1V
Then what input voltage is -3dBFS???

 

[Alan_Nesta]

dbFS question

first question: yes
second one: db=20log(vin/fs)
so you can get vin=0.707 is -3dBFS