Quote Originally Posted by Gusse View Post
This not really solution for your problem but why you have so big RC time constant for filter?
PWM cycle time for 8MHz is ~2.5ms.
39kOhm and 100nF:
Attachment 4358

How about something like this or in that range?
10kOhm and 10nF
Attachment 4359
BR,
-Gusse-
Hi Gusse,
It was a choice between really fast response or a steady output to replace a resistor network and switch. This app. didn't need the speed but really good filtering.

Terry,
It looks like the LM6482 should work for you. Taken from data sheet:
3.0 RAIL-TO-RAIL OUTPUT
The approximated output resistance of the LMC6482 is
180Ω sourcing and 130Ω sinking at VS = 3V and 110Ω
sourcing and 80Ω sinking at Vs = 5V. Using the calculated
output resistance, maximum output voltage swing can be
estimated as a function of load.
Unless... your output load is 1K then that would explain your 0.5V loss.