Olin Lathrop wrote:
...
> PWM can still be used to create the analog level, but it
> should be filtered so that the ripple at the Peltier device
> is small compared to the maximum voltage.  A better scheme
> is to filter the PIC PWM output to make the reference signal
> for a switching mode current source.

   Also PIC with few resistors will make the reference
signal. Eight levels are more then enough in my opinion.

   Mike.

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