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Why don't they use zener diodes in high frequencies?

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2 Answers 2

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In reverse biased mode, which is how you would normally use a zener, the capacitance is tens to hundreds of picofarads. This could be enough to attenuate your signal significantly, depending on the frequency and source impedance.

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  • \$\begingroup\$ The large-ish capacitance of a Zener is one of the reasons they need alternative architectures for ESD protection on very high-speed data lines. \$\endgroup\$
    – ajs410
    Apr 20, 2011 at 16:48
  • \$\begingroup\$ @Martin- Is there a relationship mobility of holes in PN junction? \$\endgroup\$
    – Cell-o
    Apr 21, 2011 at 20:55
  • \$\begingroup\$ @Cell-o, you'll have to look that up. As a practising engineer, I haven't had the need to use zeners with anything approaching RF so the theoretical reason for the capacitance isn't something that springs to mind. \$\endgroup\$
    – Martin
    Apr 22, 2011 at 15:08
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Zener diodes aren't typically used in a signal path. You won't find them easily in lower frequency paths either. They're used mostly to control DC voltages.

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