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SRF and Operating frequency for inductor

John.Jin1990

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Hello,
As a rule of thumb the SRF of an inductor should be higher than the operating frequency. I need to know why this inductor has lower SRF and why the operating frequency is much higher than SRF.

As I know the inductor and a chock are the same for using them with the same inductance and SRF. How is it possible the WA8514-AE(SRF<250Mhz) inductor is used as a RF chock for this application which frequency can be up to 2.7Ghz.
 
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vfone

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WA8514-AE is a choke, and its duty is to block higher frequencies while passing DC current and lower-frequencies.
Is doing this job providing high-impedance to the passing RF signal.
WA8514-AE have greater than 1k impedance for frequencies between 30MHz and 3GHz (with a maximum of about 22k at SRF = 200MHz).
So it will work fine in the Minicircuits MMIC PHA-202 as an output choke for frequency range 30MHz-2.7GHz.
 

FvM

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The example shows that the rule of thumb doesn't work in all situations. You should realize that the parallel resonance happens on a very high impedance level, with a capacitance as low as 70 fF.
 

biff44

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it is a special "conical shape" inductor. that data sheet has a poor picture, so you can not see that the coils of the inductor have a varying diamteter. So while ONE loop of a coil might resonate at your specific frequency of interest, the coil before it is slightly smaller and does not resonate, and the coil after it is slightly bigger and does not resonate there.

These sort of "inductors" are used for biasing up broadband devices, like a laser diode working from DC to 40 GHz.
 

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