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ADA4961 output inductors

Question asked by gavint on Nov 8, 2016
Latest reply on Nov 8, 2016 by bsam



I have two questions about the output inductors for the ADA4961.


1) According to the ADA4961 datasheet, the recommended output inductors are Coilcraft 0805CS-471XJLC. The reason given in the datasheet is: "The self resonant frequency of these inductors is high enough so that it does not impact the performance of the ADA4961 at up to 4 GHz."


I had a look at the datasheet for these inductors and see that the typical SRF is given as 375MHz.


I must be missing something, but I don't understand how a SRF of 375MHz is "high enough" not to impact the performance at up to 4GHz.


If possible, please provide an explanation as to what the datasheet means regarding the SRF.



2) These inductors are physically quite large (0805 footprint). Coilcraft offer 470nH inductors in an 0402 footprint (see 0402DF-471XJRU). What inductor datasheet parameters should I be checking if I wanted to change to a smaller footprint inductor because of space constraints?