Servo amplifier for DC motors
What is best circuit for servo amplifier of DC motors?


I'd use a PWM converter that feeds to a push-pull MOSFET output stage. You could probably use a power op-amp circuit but you'd be running it hot although it would still work. Your power supply should be OK if it can supply 30V at 6A. For a circuit I'd consider looking at the LT1160 data sheet. It has the following circuit for a 200W class D amplifier. 



It needs checking what components other than the one I marked that needs bypassing to allow proper DC control but this would be a good starting point I reckon.

A pointer about terminology - a servo amplifier is more than a simple amplifier like what you have in your diagram. A servo amplifier takes the demand input and processes the feedback signal to ensure the motor is kept in closed-loop control

Wiki has an article.

I also asked in my comment about the lowest speed demand and the number of notches in the disk. I asked to make sure you were properly accounting for low speed running in the loop filter.