[sdiy] LM13700/LM13600-based filters

[Antti Huovilainen]

On Mon, 26 Apr 2010, Tom Wiltshire wrote:

> One thing that jumps out at me is that very few designs use the darlington 
> buffers, mostly preferring to use a standard op-amp buffer instead (some 
> examples below)
>
> Can anyone tell me what the problem is with the on-chip buffers? Why not 
> use them if they're there? Are they *that* awful?!

They weren't present in the CA3080 and people seem to blindly copy those 
old designs. For cases where you need very high impedance, the buffers 
aren't that great, but for normal audio filters they should work just 
fine.

LM13700 could be used to build a dual voltage controlled ADSR too. All you 
need is to think of the EG as a filter with switched input and control 
signal and the rest is dead simple.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova