[sdiy] Saw DCO

[Richard Wentk]

At 19:42 06/10/2004 +0200, Magnus Danielson wrote:

>Actually, what I would do is set up another OTA and maybe an op-amp to create
>a separate control loop for the amplitude.

Why? I don't get what the advantage of this is over using a preset 
digitally computed curve via a separate DAC/DAC output to control level.

Since it's a non-precise kind of application it would be easier to use a 
spare 3080 (or use a dual OTA of some other sort for exact matching) to 
finagle a temperature compensation current value and add/subtract this from 
the level drive current directly. With no loop and no time constant to 
worry about, instantaneous error will be much smaller. And for a dual OTA, 
matching would guarantee accurate temp tracking.

Richard