[sdiy] New OTA

[John Blacet]

You need to study the data sheet here. This is actually well planned or 
a lucky accident.

Use an inverting op amp stage to sum (100Ks) your front panel pot and 
jack CVs. (Standard stuff).

Add one more 100K to add -10V to the mix. This should be an accurate 
stable voltage (LM4040 for example). Also use the inverted 10V (+10) for 
the pot leg 3.

Select your feedback resistor for the desired control range, such as 33K 
for 100 dB.

Now everything goes the right direction. You needed the summing amp 
anyway! The stable voltage reference is a plus since it can be processed 
for use elswhere in the module. You need stable and accurate since the 
control is 33mV/dB.

Aaron Lanterman wrote:

>
> On Tue, 26 Jul 2005, John Blacet wrote:
>
>> You can do just about anything that you need to do OTA wise with the 
>> Analog Devices SSM2164. Quad for under $4 each. Still production in DIP.
>
>
> Reading over the 2164 data sheet, am I imagining things or does the 
> control go the wrong direction? (I remember Dr. Mabuse mentioning 
> something about that).
>
> - Aaron
>
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>
>
> Dr. Aaron Lanterman, Asst. Prof.       Voice:  404-385-2548
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>

-- 
Regards,
John Blacet

Blacet Research
http://www.blacet.com