> I'm trying to figure out how to generate a range of voltages between 0
> and 150mV in 30mV steps (ie: 0, 30, 60, 90, 120, 150 mV).

What accuracy?  What response time?

> I have pondered two methods so far but I am sure there is a simpler
> method of doing this.
>
> First method is to setup a PWM output to an RC filter with a unity gain
> op amp for buffering. I've never done this before and everything I read
> on PWM shows it operating in the 5V range. Maybe a scaling op amp on the
> output?

You don't need an opamp to scale a 5v signal to 150mV, just two resistors.
This is only one resistor more than needed by the first R/C filter stage,
so is easy to do.

One possibility would be a 47Kohm resistor in series with the PWM output,
with a 1.5Kohm resistor after it to ground.  That would give you slightly
more than 0-150mV output range, with the final adjustment done by
selecting the proper PWM value.


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