# Zener Diode - Amizone Zener Diode Zener-Diode Voltage-Regulator Circuits 1 The Zener Diode * Zener diode is designed for operation in the reverse-breakdown region. * The breakdown voltage is controlled by the doping level (-1.8 V to -200 V). * The major application of Zener diode is to provide an output reference that is stable despite changes in input voltage power supplies, voltmeter,

2 2 Zener-Diode Voltage-Regulator Circuits * Sometimes, a circuit that produces constant output voltage while operating from a variable supply voltage is needed. Such circuits are called voltage regulator. * The Zener diode has a breakdown voltage equal to the desired output voltage. * The resistor limits the diode current to a safe value so that Zener diode

does not overheat. 3 Given : the Zener diode I - V curve, R 1k Find : the output voltage for VSS 15 V and VSS 20 V KVL gives the load line : VSS R i D v D 0

From the Q - point we have : v o 10.0 V for VSS 15 V v o 10.5 V for VSS 20 V 5V change in input 0.5V change in v o 4 3 Load-Line Analysis of Complex Circuits

* Use the Thevenin Equivalent 5 Given : Zener diode I - V curve, VSS 24V, R 1.2k , R L 6k Find : the load voltage v L and source currents I S RL R RL Applying Thevenin Equivalent VT VSS

20V , RT 1 k R RL R RL VT RT i D v D 0 v L -v D 10.0 V I S (V SS - v L )/R 11.67 mA

6 Given : the circuit and the Zener doide I - V curve as shown. Find : the output voltage vo for i L 0, i L 20mA, and i L 100mA 7