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

[Scott Gravenhorst]

=?iso-8859-1?Q?Ren=E9?= Schmitz <uzs159 at uni-bonn.de> wrote:
>Hi Ian, Hi Martin!
>
>>Of course, in the end you have to look at the whole picture and also work 
>>especially hard at the "weakest links".
>
>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.
>
>>But you have to understand all the problem areas and what the limits are in 
>>each area before you can do that.
>
>Exactly. 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.)

Wow.  Well, if I follow the thread correctly, René, you've done this! (and I
built [and use] a copy of the circuit).  You put together a very simple VCO
using a 4069 gate for an integrator.  For what it's worth in this discussion,
I got 9 octaves of linear operation out of such a "poor integrator".  It seems
that even a poor integrator is sufficiently accurate for musical use.  For me,
it casts doubt on whether the other much smaller influences are worth
investigating at all.


>>I thought Martin did a nice job of laying all this out.
>
>Of course! And I should say that I never took some of these points into 
>consideration. The temperature effects of open loop gain for example.
>
>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. 
>
>Cheers,
> René
>
>
>-- 
>uzs159 at uni-bonn.de
>http://www.uni-bonn.de/~uzs159
>
> 
>
>
>

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