# Tunnel diodes Zener breakdown

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

• 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. Mar 24 '21 at 18:20
• I guess not current gets too high. Mar 24 '21 at 18:21
• 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. Mar 24 '21 at 18:24
• They seem to conduct Ip (~1mA) at at few tens of mV reverse voltage. Mar 24 '21 at 18:25
• @SpehroPefhany aren't those the backward diodes? Mar 24 '21 at 18:27

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

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.

• Surely when under positive bias that's the normal diode conduction. The reverse conduction is Tunnel breakdown which occurs much lower than Zener breakdown. Mar 24 '21 at 19:53
• @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.
– Matt
Mar 25 '21 at 0:10
• @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. Mar 25 '21 at 0:33
• @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.
– Matt
Mar 25 '21 at 2:56
• @Matt. I'm sorry. For some reason, I thought you were the poster. Mar 25 '21 at 13:52