 An amplified Zener regulator controls voltage levels across a circuit. The regulator gets its name from its primary component, the Zener diode. The Zener diode is a fixed diode that maintains a given voltage value, no matter what the unregulated DC input might be. In this demonstration, we'll put 20 volts and use a Zener diode with a value of 5 volts. The regulator circuitry also contains a silicon series pass transistor. Remember that in a transistor, the voltage value at the emitter is always 0.7 less than the voltage at the base. The base of this transistor is connected directly to our 5-volt Zener diode. Keeping in mind the rule of 0.7, we can determine that the output voltage at the emitter will be 0.7 volts less than the voltage at the base or 4.3 volts. Therefore, the voltage level at RL load resistor will also be 4.3 volts. This variance in voltage levels facilitates the flow of current through the circuit. Now, if we change the Zener value, observe how the transistor drops the value down 0.7. So at the emitter and the RL load resistor, we see a voltage that is 0.7 volts less than what the Zener diode permits at the transistor base. Thus, if we change the Zener diode value to 10, then the voltage at the transmitter base is 10 volts. After passing through the transistor, the voltage drops to 9.3V, resulting in a 9.3 volt load at the RL resistor. With a Zener diode value of 15 volts, you'll have a 14.3 voltage at the emitter and the RL resistor.