How to calculate Q factor on a fit Gaussian/Lorentz curve

[ethen99]

Hi

I can use LabVIEW non-linear / gaussian peak functions and do a curve fitting on my X/Y data . Is there any function that can help me to find +/- 3db for calculating Q factor ?

[Bob_Schor]

If you are measuring power (not amplitude), 3 dB is approximately one half.  So if you plot power as a function of frequency (perhaps on a log-log plot), and find that the peak has a value of, say, PeakValue, then the ±3 dB points will be where the Gaussian curve you fit has the value of PeakValue/2 (one to the left of the peak, one to the right).

Bob Schor