[sdiy] integrator / capacitor leakage

[Grant Richter]

I think the answer is so obvious, it is hard to see.
Any multiplication (amplification) of the integrator output will  
multiply the errors by the same factor.

So, commutative axiom says:

(Signal + Error) * 10 = (10 * Signal) + (10 * Error)

Since calculus is built on algebra, if you put an integral sign in  
front of terms, it is still axiomatically correct.

Think of it as signal to noise. Best bet is to maximize signal level  
to begin with.
Also, more parts just means more sources of error.

Plus and minus 10 volt swing is normal for op-amp powered from +/- 15  
volts.
I would optimize integrator performance by part selection.
For 20 kHz top end you will need to slew 20 volts in 50 microseconds.
That is 0.4 volts per microsecond. Not demanding by todays standards.


On Dec 3, 2005, at 6:47 AM, JH. wrote:

> Thanks for the opamp hint.
>
> But for a given set of parts (opamps, caps, etc.), would
> running the VCO at lower level, and then amplifying, have
> any advantage or rather not?
>
> JH.
>
>
> ----- Original Message -----
> From: "Grant Richter" <grichter at asapnet.net>
> To: "Synth DIY" <synth-diy at dropmix.xs4all.nl>
> Sent: Saturday, December 03, 2005 6:44 AM
> Subject: Re: [sdiy] integrator / capacitor leakage
>
>
>>>
>>>
>>> Good amplifiers are easier to find.
>>>
>>
>> Burr Brown used to make an amplifier in the pico-amp input bias
>> range. OPA404 (EOL I bet)
>>
>> http://www.compel.ru/pdf/TI_BB/OPA404.pdf
>>
>> They recommended cleaning the chip with IPA to get finger oils off.
>> Contamination from handling chip was enough to throw integrator TC  
>> off.
>>
>>