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ADIsimPLL legacy active filters

Question asked by mrln55 on Aug 3, 2014
Latest reply on Aug 7, 2014 by mrln55

In using ADIsimPLL to design a signal source using the ADF4002 and Mini-Circuits JTOS-50, I selected the AD820 for an active loop filter in the CPA_FPB configuration. There were no errors or warnings generated during the simulation and the the results of the simulation (see attached) met my requirements. However, in delving into the help file, I found the following caveat:

 

Legacy Inverting Active Filters:

 

These configurations are not recommended for design as the lack of prefiltering exposes the op-amp to the short current pulses from the phase detector.  The op amp is unlikely to be able to respond to these in a linear fashion and poor performance may result.   Use of the preceding similar prefiltered designs are recommended instead.


Should I discard the circuit boards that have been fabricated based upon the simulation and use a different active filter configuration, or can I trust the ADIsimPLL simulation results with the AD820?

 


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