S
Stanley
Guest
hi all,
I was using hspice to simulate a serial of OP Amps.
After long time of trying the .FFT command with different parameters,
I think I can get a reliable THD result with close harmonic pikes on
the spectrum and an almost-fixed .FOUR result.
(is this right??)
But the noise floor shifts with different .FFT command.
from -230dB(almost nothing), -160dB, -120dB, maybe -80dB.
So how can I trust the result. The highest one or the lowest one?
Or I can't get an accurate noise floor by spice basically?
What is the best way to use .FFT? the longer time the better? the more
dft points the better? Thank you.
Stanley
I was using hspice to simulate a serial of OP Amps.
After long time of trying the .FFT command with different parameters,
I think I can get a reliable THD result with close harmonic pikes on
the spectrum and an almost-fixed .FOUR result.
(is this right??)
But the noise floor shifts with different .FFT command.
from -230dB(almost nothing), -160dB, -120dB, maybe -80dB.
So how can I trust the result. The highest one or the lowest one?
Or I can't get an accurate noise floor by spice basically?
What is the best way to use .FFT? the longer time the better? the more
dft points the better? Thank you.
Stanley