Led as Zener diode? possible?

[keko]

I read somewhere it could be done, but don't remember where.

Can a led be used to sub a zener? Any zener? I see they go from a few volts to up to 30v!

[javacody]

yes, I just built Runnoffgroove's Peppermill, and it uses this trick.

[keko]

ah..that's were I saw it.

but what about the zener's rating? I see in the pepermill, and now on the amz boost (my next build, the reason for this post, I guess) that the diode is used to prevent static electricity damage to the mosfet. Is that the only reason why a LED could be used?

thx for the fast answer javacody (is that as in java coder?)

[GuitarLord5000]

I'm pretty curious about the diode on the peppermill myself.  Should this LED be used for most mosfet circuits?  I'm fixing to try to roll my own distortion with mosfets and am taking this into consideration.

(and perhaps cody just really likes coffee?)

[javacody]

My first name is Cody, I program in Java, and I love coffee (a pot a day). Is that a trifecta? Not all of us can think up cool names like "GuitarLord5000"!  LOL

I think that the led does the same thing that a zener would do in this instance, which is provide protection to the MOSFET from static electricity. LED's are quite a bit easier for me to lay my hands on that zeners (in fact, I have about 100 assorted LED's) and its one less part that I have to keep on hand. Too bad there isn't some way to light it up at the same time.  

[Ansil]

joedavissons obsidian  one of the original n channel mosfet schematic had  a red led in it. for this purpose

[Peter Snowberg]

Zeners conduct like a regular diode in one direction and they have a known reverse breakdown voltage in the other. You're much better off biting the bullet and getting a 9.1V Zener for maximum protection. You could get away with using enough diodes to get a higher forward voltage than you will ever see from the gate to the source (bias + signal) (use blue for the least parts required), and then add another regular diode in the opposite direction and in parallel with the string of LEDs. If you don't add that second diode, you may be only 1/2 protected.

Just my 2 cents.

Take care,
-Peter