Q factor

[jason]

Hello All

Say Impedance Z i = jwL + Rs
(Rs is in series and it is actually the internal series resistance,
this means inductor is an ideal one)

So if we assume this way, then does it mean jwL comes from the ideal
inductor? Not from any of the Rs at all?

If we want to find Q of the inductor
we will use Q= wL/Rs where SL(or jwL) is not involved totally in the Q
equation.

Am I right ?
Kindly enlighthen
Thank you


Jason

 

[Tim Wescott]

jason wrote:

Hello All

Say Impedance Z i = jwL + Rs
(Rs is in series and it is actually the internal series resistance,
this means inductor is an ideal one)

So if we assume this way, then does it mean jwL comes from the ideal
inductor? Not from any of the Rs at all?

If we want to find Q of the inductor
we will use Q= wL/Rs where SL(or jwL) is not involved totally in the Q
equation.

Am I right ?
Kindly enlighthen
Thank you


Jason

If your actual inductor acts exactly like a perfect inductor in series

with a resistor yes. Otherwise no. Many times in RF work your actual
inductor will either act like it has both series and parallel loss, or
(probably closer to reality) like it's transformer-coupled to a lossy
circuit. This is why if you plot the Q of an inductor against frequency
it'll come to some broad peak then slip down again.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Mark]

The RF sereis resistance goes up with frequency due to the skin effect
so this alone can cause the Q to level off and decline at higher
frequencies giving the broad peak.

Mark