LED as diodes - 3mm or 5mm?

[Outlaws]

If I wanted to use an LED for a diode, then can I use a 3mm?

I have a couple 3mm LEDs that I pulled out of an old DVD player.  They light up with normal 4k7 resistors.  But is the clipping going to be different than a 5mm?  Will there be voltage problems?  Anything?

[phillip]

The 3mm LEDs should pretty much work the same as 5mm, since the forward voltage drop on LEDs is usually pretty consistent.

Phillip

[LivingDeadPunk]

Depends on the circuit you're building, for example in a Guv'nor you will use 3mm red diodes (why red??? I don't know) not 5mm, I think most of the time it's just that 5mm led are too big, I may be wrong though.

Does someone knows why the Guv'nor leds have to be red :?:

[the_badcliff]

different color LED's have different voltage drops.  In distortion circuits a higher voltage drop usually means less distortion and more clean headroom.

I think red LED's have a 1.2V drop, in general, it might be 1.8V though, I forget.

Compare this to a germanium diode which is .3V, or silicon which is .7V.

I think other colored LED's have an even higher forward voltage than red.  Anyway, all these are pretty well documented in their datasheets, and/or can be looked up in the forum.