AVR-Chat

Anurag Chugh wrote:
> why only PWM?.. why not use an R2R ladder instead with precision 
> resistors...
> i know they would hog a whole PORT but arent they easier to implement ??
> and they can do DC output values too... a simple opam in front (voltage 
> follower) will boost current output too...
>  
> i am sure most people dont use R2R... but please tell me why?? i know 
> there must be a reason...

R2R is a high component count and uses more space (16 resistors) compared
to one RC filter DAC. The RC filter DAC also does DC output. R2R needs
high tolerance resistors to guarantee monotonicity, but that can be
undone if there are differences between the pin driver voltages.
R2R is better for high-speed things.