I am trying to make a motor driver, similar to a H-bridge using four tip 121 (the label in the schematic below is wring because I could not find a tip 121 at my B2 simulator) the schematic is this:
B2 and the switches represents my arduino's pins.
The problem is that I only get 5V at the motor... even when the power supply is 12V! It does happen in the simulator, but I have no clue about why it happens...
Googling I found that the schematic of the L298 (the IC used in many arduino shileds/motor drivers) is quite similar to mine... But I do not understand why I only get 5V at my motor... As far as I understand the voltage drop at the collector-emitter of a transistor is constant...
What (and why) is wrong with my design?