Do tunnel diodes exhibit Zener breakdown? Since tunnel diodes are more doped than Zener diodes they should, but I am unsure.

  • \$\begingroup\$ Ask yourself - are you running a tunnel diode with a reverse bias? Then go onto google and see why that question is important for zener breakdown. \$\endgroup\$
    – Andy aka
    Mar 24 '21 at 18:20
  • \$\begingroup\$ I guess not current gets too high. \$\endgroup\$
    – Miss Mulan
    Mar 24 '21 at 18:21
  • \$\begingroup\$ They'll certainly have a breakdown voltage, and probably not an impressive one. I wouldn't purposely operate one there, because I know that (A) a bog-standard 2N2222 or 2N3904 has a pretty reliable 6V zener breakdown in it's base-emitter junction, and (B) the standard advice from amateur radio circuit designers is that once you've pulled one out of your junkbox and used it as a zener, you shouldn't use it as a transistor any more. \$\endgroup\$
    – TimWescott
    Mar 24 '21 at 18:24
  • \$\begingroup\$ They seem to conduct Ip (~1mA) at at few tens of mV reverse voltage. \$\endgroup\$ Mar 24 '21 at 18:25
  • \$\begingroup\$ @SpehroPefhany aren't those the backward diodes? \$\endgroup\$
    – Miss Mulan
    Mar 24 '21 at 18:27

The typical IV curve of a tunnel diode shows that the breakdown voltage is positive:

enter image description here

That's from the RCA Tunnel Diode Manual that I linked to in my answer to one of your earlier questions about tunnel diodes.

The solid curve is from a normal diode. A Zener diode breakdown would be similar.

The tunnel diode hits breakdown at a positive voltage - tunnel diodes conduct in reverse mode, always.

  • 1
    \$\begingroup\$ Surely when under positive bias that's the normal diode conduction. The reverse conduction is Tunnel breakdown which occurs much lower than Zener breakdown. \$\endgroup\$ Mar 24 '21 at 19:53
  • \$\begingroup\$ @KevinWhite Yes, you are correct. In increasing forward bias a tunnel diode has tunneling current, then that current is suppressed when the bandgap overlap closes, then regular forward conduction takes over at higher bias. \$\endgroup\$
    – Matt
    Mar 25 '21 at 0:10
  • \$\begingroup\$ @Matt - I don't understand your statement "breakdown voltage is positive". In the curve shown the implication is that positive is to the right. Also, you are showing the curve for a backward diode, not a normal tunnel diode. \$\endgroup\$ Mar 25 '21 at 0:33
  • \$\begingroup\$ @KevinWhite I am doing none of those things, this is not my answer. However I disagree on one point, this is the IV of a tunnel diode. Where do you take exception? Backward diodes and tunnel diodes are very similar, and this exhibits the characteristic negative resistance region of a tunnel diode. \$\endgroup\$
    – Matt
    Mar 25 '21 at 2:56
  • \$\begingroup\$ @Matt. I'm sorry. For some reason, I thought you were the poster. \$\endgroup\$ Mar 25 '21 at 13:52

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