I am using PWM from a micro-controller to drive a DC motor. I know how to design amplifiers: common emitter, common collector, common base. My problem is, I don't know how the motor will act as a load when I attach it to the final stage. I don't know much about DC motors. I am using http://www.pololu.com/product/2271 and I have a TIP142. My thought process is that, I should make a common emitter to amplify the PWM to 6V and feed it to a common collector to get the current needed to drive the motor. I'm not sure how to make the common collector since I don't think I can treat the motor as a simple resistor.