Voltage regulator with Zener Diode and Transistor

To get around the power limitations we use a series-pass transistor. In Fig. 5 a NPN transistor with a Hfe or DC gain of 100 in effect "multiplies" 1mA from the Zener-resistor circuit to 100mA. The reason I went to a 5.6 volt zener is to compensate for the 0.6V drop across the B-E junction of Q1. Yes you need the 100uF capacitor to assure power supply ripple doesn't cause problems. As we draw more load current 99% of the current originates with Q1.