How do I make a voltage switcher using transistors?
For 3V voltage droping the switched regulator does not have much advatage over classic resistive way because of switched regulator efficiency (about 80%). For higher drop they are good choice.
Here are the three examples, in first you must know the load resistance to calc the shunt. In second and third you dont need it. The second is based on a constant voltage drop of diode (0.7v) where four diodes in series creates about 2.8v drop. The third one uses a 10v zener diode to hold a 9.3v constant voltage over the load (the 0.7 is lost on BE junction).