[sdiy] synth uses for LM3909

[Roy J. Tellason]

On Thursday 13 January 2005 05:30 pm, anthony wrote:
> >> and see if they had them at Mouser. It's like $11.50. That seems like a
> >> lot for such a simple little chip.
> >
> > That's absurd.  Perhaps it's no longer being made?
>
> The part was an NTE replacement part, but those are usually relabled NOS
> parts (like the CA3080's I just bought - you can see the old markings below
> the NTE 996).

That accounts for at least part of it,  since replacement parts like those 
tend to be more expensive overall than OEM numbers...

> >> So should I just cherish fond memories and say goodbye to the LM3909 and
> >> just stick with 555's (and 556's and 558's)?
> >
> > The biggest advantage to using one of those chips is that you could get a
> > flashing LED that would run off a _single_ 1.5V cell.  Other than that
> > there
>
> Yeah and I think you can do that with the CMOS version of the 555 - 7555 or
> TLC555.

I don't see how,  as even if the chip would operate down that far it still 
needs to put out a higher voltage than what it's getting in on the power 
supply pin.  I don't know of any 555 versions that do that!

> If you wanted to you could make anything run on 1.5V - just make a voltage
> multiplier out of a 4011 or 4069 and some diodes and caps.

Yeah,  though I'd find it easier to make oscillators with one of the 
schmitt-input gates.  But that's more parts,  the 3909 offered a single-chip 
solution (though yeah,  you did need a couple of caps with it).

>You could even make it pretty small with tantalum caps and SMD's. A lot less 
> smaller than another battery which would offset increased drain probably 
> depending on the app.

I dunno...  <shrug>

As far as making stuff and SMD,  I'm not gonna go there.

> But I digress...
>
> What made me think about it was somewhere on the carrionsound website he
> mentioned making a version of the Lumivox with an LM3909.

Hm.