[sdiy] OTA question

[Paul Perry]

Did you manage to get it to a very low frequency when you were
testing with a pot and a 22K resistor?
And if you did, was the waveform shaped OK then?

paul perry Melbourne Australia

----- Original Message ----- 
From: "Tim Parkhurst" <tim.parkhurst at gmail.com>
To: "Ian Fritz" <ijfritz at comcast.net>
Cc: "synth-diy" <synth-diy at dropmix.xs4all.nl>
Sent: Monday, August 30, 2010 8:43 AM
Subject: Re: [sdiy] OTA question


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
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