Stepper motor control circuit

For my stepper motor controller I’m using a CD4050 non inverting buffer, output of the Arduino Uno to input of the CD4050 and the output of the CD4050 to drive a TIP120. The Tip120 will apply the ground to complete the coil circuit on the stepper motor. I will put a 1N4001 diode across each coil. I will have four each circuits driving the motor. The motor I’m using is a 3.6V, 2 amps unipolar. I know the TIP will handle 2 amps, but what amp power supply do I need? The way I’m running the stepper is I turn on one coil at a time. I would think a 3amp supply would be more than enough. Think this will work?

I hope you find this Useful.

Is there any reason why you are not using an "off the shelf" stepper motor driver and saving yourself all the trouble of making one from discrete components?

Can you provide a link to the specifications for the stepper motor you are using?