[sdiy] mosfet/cmos opamp

[David G. Dixon]

> Whether "any of them will do for S&H" depends on how large a cap you
> use.  You are using 100 nF.  I am using 5 nF, in order to be able to
> charge
> it in 30 usec. So I disagree with your conclusions by a factor of 20.  :-)

Yes, but the charging time also depends on the on-resistance of the switch.
I'm using DG409, with a typical on-resistance of 40 ohms.  Assuming a
charging time of 2.2RC, then in my case it's about 2.2*40*100/1,000,000,000
= 8.8us -- call it 10us.  Even at the stated maximum of on-resistance of 100
ohms, it's still less than 25us.  (Is this correct?)