integrators or followers

[Martin Czech]

:::The only real benefits I can see is that the OTA output operate towards a 
fixed
:::voltage level (the virtual ground) which may be beneficial for their output
:::stage. As I recall it some OTAs will get degraded preformance as you move the
:::operating point of the current output so a current follower is needed and
:::recommended. But instead of using a resistor you just stuff your cap in and
:::you got your integration operation as you wished to have it.
:::
:::Another fully valid reason is that this is the cheapest way of getting
:::an inversion since you anyhow must buffer the output of the capacitor, so the
:::op-amp must be there anyhow, so just setting it up diffrently makes it do the
:::inversion for free.

One disadvantage of using an integrator is that a "set" feature causes
more trouble... Setting a cap to some voltage needs only one MOSFET,
and one can do this with pretty low leakage, if you use the voltage follower
output as bootstrap voltage to minimise the voltage across the MOST,
you know this serial 2 MOST circuit...

There is only one junction more at the cap.

Setting an integrator is a known circuit, but things get more complicated,
basically you switch in two resistors in order to make the integartor appear
like a inverting summing amp...

I think a set feature is usefull, for attack control of vcos,
voltage controlled phasing/syncing, and for VOSIM like oscillations.


m.c.