[sdiy] expo accuracy? or integrator accuracy?, or both?

[Ian Fritz]

Hi Rene. Maritn. et al. --

At 12:35 AM 2/9/2003, René Schmitz wrote:

>Sure you have to identify the areas where you can the largest improvements.
>But for that, you will have to do it for _all_ of them. That was the whole
>point.

Well, we agree then. (Of course)

>  Perhaps a good thing to see what the effects of open-loop gain,
>amplifier input bias and open-loop output impedance are, is to make an
>oscillator with a relatively poor integrator. One that satisfies these
>criterions is the CMOS inverter for example. By choosing that, one actually
>can make real measurements and actually see the effects of these parameters.
>(Since a simulation will get you an answer, but not necessarily a valid one.)

Good idea.  Another trick that can help track down drift sources is to 
apply heat locally, although that won't separate the different effects 
within an opamp, of course.

>My comments were merely aimed to also include the rest of the circuit into
>the consideration. The question here is what effects exist in CCOs (and not
>just integrators) and whether they affect the overall circuit performance.

Agreed.  I especially appreciate the reminder that the discharge switch 
leakage can easily obviate the advantages of a low leakage op amp 
integrater.  Your use of the two-FET trick in your VCO 3 gives a good way 
to attack that problem.  How much residual leakage you get with that 
approach and how it depends on temperature is not obvious to me, since 
leakage is usually speced at a very high voltage. This could be looked at 
further.

Best regards,

   Ian