Starting with a 1.2uH inductor results were immediately satisfying. The measured L and variation with frequency matched the curve shown in the TDK datasheet. And the self resonant frequency was readily measured as 180MHz.
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| 1.2uH Inductor |
Let's try an unknown but small 0603 wire-wound chip inductor. Measured as 22nH.
How small can we go? I have some 12nH 0201 chip inductors with factory measurements (sample size, variance etc). Wow. 12nH measured.
Previously I have used a signal generator and test fixture with a
measured parallel capacitance
( 112pF from memory ) to measure the
resonant LC frequency, then back calculate what L was. This worked very
well down to nH sized inductors. With a power detector I was also able
to estimate Q by sweeping around the resonant frequency for the -3dB points.
The NanoVNA is
now my preferred approach. I prefer the fixture without the 50 ohm resistor. The curves are easier to see and therefore interpret. Either fixture is fast to use and easy to see how L changes
with frequency. I can't see how Q can be measured, but A/B comparisons
show slight differences. The higher the inductor Q the closer to the edge of the
Smith Chart.
Go on, give it a try.
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