Recommended SMD ferrite bead value for FB1 in 6GHz frequency counter LM2940 circuit?

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#1 21682722 12 Jun 2019 23:14

Peter Evans Peter Evans

Anonymous

Post #1
21682722 12 Jun 2019 23:14

I'm just getting round to constructing the 6GHz Frequency counter (Oct 2018).
My question relates to the SMD noise filter ferrite bead (FB1) from the 5v regulated output from the LM2940 regulator. In the parts list it is described as a 'low-resistance SMD ferrite bead (3216/1206)'.I have attempted calculating the inductance 'L' required (from L=X/2
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#2 21682723 12 Jun 2019 23:28

Alan Winstanley Alan Winstanley

Anonymous

Post #2
21682723 12 Jun 2019 23:28

Hi, your query hasn't posted correctly, and algebraic symbols might not appear correctly in HTML posts. The best way will be to email to us so that we can forward it on to the designer in the hope of a response. It's pe(_at_)electronpublishing.com
ThanksAlan W
#3 21682724 12 Jun 2019 23:45

Peter Evans Peter Evans

Anonymous

Post #3
21682724 12 Jun 2019 23:45

Thanks Alan - it seems to have cut everything from the -'pi' symbol (L=X/2.pi.f) from my query.
I was just wondering what the value of frequency I should use that constitutes noise to find L & the associated impedance.Or am I missing something obvious and there is a general rule of thumb that should be used when selecting a noise filtering ferrite bead? The only one I have in my spare bits bin is 47ohm at 100MHz.
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