Running DC motor with square wave
- Purple signal is the voltage at the transistor base, referenced to the common ground
- Yellow signal is the voltage at the transistor emitter, referenced to the common ground
- Notice the spike in the voltage when the transistor is turned off. This is due to an inductive component (DC motor) acting like a current source when the magnetic field is collapsing. With the current trying to force its way through the transistor, high voltage builds at the emitter.
Mitigating inductive spike with a diode (Snubber)
- A diode can provide a conductive path for the current from the motor. This way, a lower voltage is sustained.
- The diode in this circuit is a common 1N4007, and it is connected parallel to the motor.
