However, I need the motor to keep running when the pwm signal is zeroed. What I have now is roughly 0-5v amplified to 0-Nv, but what I need is to add a DC offset so that the motor is controlled from ~4-Nv. I could of course just adjust the PWM signal but I would prefer to keep the resolution of the PWM signal.
Could I just add a DC offset with a voltage divider after the amplification stage? I'm guessing an op-amp would not be good at handling the current draw and possible flyback from the motor so I'm thinking a op-amp summing circuit is out..