EVAL-ADAU1452REVBZ

Hi,

The customer has implemented the peaking filter transfer function in Python, and has a question. It appears that the peaking filter maximum is twice that of the gain that they have set. For example, if they set the gain to 2 dB, what is graphed shows a peak at 4 dB. See attached image for example.

They have been through the documentation for the Robert Bristow-Johnson method, and believe that there maybe some discrepancy in the definition of A with the wiki page (here) . For example, it is stated as:

A = 10^(dbGain/40) in the documentation.

But the Analog Devices Wiki page states:

gainlinear = 10^(gain/20)

where one assumes that the variable "gainLinear" refers to the variable A in the subsequent equations (since A isn't defined anywhere else on the wiki page)

When they change the definition of A in their script to match that of the Robert Bristow-Johnson method, the peaking filter has the correct gain (where gain was set equal to 2).

Could you please confirm that this is the case?

Thanks,