Low-C input protection diodes

Hello Folks,

What's the low cost and most of all low capacitance diode pair du jour for protecting RF chip inputs? My staple is the BAV99 or BAV199 but above 500MHz the 3-4pF of a pair begin to matter. Can't bias them much because there ain't a lot of VCC to begin with.

Recovery time doesn't matter as long as the stray inductance is low so the diode kicks in the nanosecond a spike wants to come in. They should be able to stomach something around an amp once in a blue moon. Series connection, of course. If it has to be singles, ok.

I was pretty surprised to learn that some RF chips have internal coupling caps but almost zilch in terms of protection. Consequently a client of mine has them die like flies. Why are RF chip inputs so fickle? For example, the Linx datasheets often just state abs max at 0dBm. Great. That's not much of a consolation for anyone who has to deploy in a rough environment.

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Regards, Joerg

http://www.analogconsultants.com/
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