[sdiy] LM13700 questions

[David G Dixon]

> Is it OK to use the current output of an LM13700 to feed the 
> Iabc pin of another LM1300?

I don't see why not.

> According to the datasheet the maximum output current is in a 
> suitable range for the Iabc. The only concern I have is that 
> the Iabc pin is referenced to the negative rail.

As long as you don't exceed the absolute maximum rating of the 13700 (2 mA
to Iabc -- 1 mA is safer) you should be OK.

> The application I have in mind is voltage control of 
> modulation amount.

This is a classic VCA application.  Why not just apply the voltage to one
OTA?  Why do you need two?

> It seems silly to convert the current to a voltage and back 
> to a current again...

It is.  I do this sort of thing all the time with SSM2164 VCAs.  You can
chain them together like a choo-choo train.