# Tag Info

5

Many of these specs are different ways of expressing the same thing. Q and ESR (equivalent series resistance) both express the loss in the capacitor. $$Q = {\left| 1 / (2 \pi f C)\right| \over \text{ESR}}$$ Strictly speaking ESR can change with frequency due to things like skin effect, but this equation can get you close enough to make a comparison as long ...

4

This is an Inrush Current Limiter (ICL). You can still get them today, but they look quite a bit different. See Digikey for a wide range of parts. Typically, these are used for reducing the inrush current of main power supply capacitors instead of filament protection, so they're optimized a bit differently. https://www.digikey.com/en/products/filter/inrush-...

4

First and foremost, varicaps aren't mechanical. If you want a rapidly tunable thing, that's a necessity; even if you just want something tunable by electronics, it's very desirable (otherwise you'll need to motorize your air gap cap...). Air gap capacitors can be made to withstand very high voltages, which makes them desirable for anything that has to handle ...

4

I bet you can make this work reliably with an SMT MLCC. You just need something bigger than an 0603. If you switch to leaded capacitors you're going to have a much harder time finding high frequency data since the lead inductance starts to become significant at hundreds of MHz. I'd suggest searching with manufacturer tools rather than distributor tools. You'...

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