[sdiy] OTA question

[Tim Parkhurst]

On Sun, Aug 29, 2010 at 1:56 PM, Ian Fritz <ijfritz at comcast.net> wrote:
> Hello --
>
> I'm working on a Tri core VCO based on a CA3080 OTA.  It's similar to the EN
> thru-zero VCO, which is up at Bernie's site.  Currently, its output is
> swinging 0 to 6 V.
>
> When I drive the OTA bias current from a pot across the PS and a 22k series
> resistor it works fine.  But when I drive it with a linear V-I converter the
> waveform at low frequencies is distorted.  The distortion makes the waveform
> dome shaped, ie, it is always curved downward.  It appears that there must
> be some kind of leakage which increases with increasing output signal.  But
> where exactly is it and why would it only show with the active drive?
>
> I've tried a couple of versions of the linear V-I converter, both of which
> are common and include a PNP transistor driving the control input pin from
> its collector.
>
> Any thoughts?
>
>  Ian
>

Hi Ian,

Have you tried a different 3080?


Tim (just a stab in the dark) Servo
-- 
"Sire, the church of God is an anvil that has worn out many hammers."
- H.L. Hastings