While the Darlington is continuously turned on and off by the PWM signal, the RC low pass filter will result in a minor ripple of the voltage on the cap. With a H-bridge output the bridge should be turned off when the voltage difference becomes lower than some arbitrary amount, depending e.g. on the ADC resolution.In the given circuit, with a 5V supply, no negative voltages can occur.
Don't forget the feedback. You need at least a digital P controller, eventually a PID controller.
A voltage follower requires feedback from the driven circuit, and thus is a controller, regardless of analog or digital implementation. It can be implemented as simple as in #10 (Proportional controller), or as a full fledged PID controller.
No.The analogue input can't read negative voltages. You have to bias it at 2.5V, so that bias is carried over when you do the read / write.
I would like to know how you are getting the 2.5v bias?
I am happy with this as a solution
but persisted a little longer thinking Arduino users would have come up with a low voltage solution to such situations? It would seem not,