25-07-2012, 10:33 AM
VOLTAGE REGULATOR
Voltage regulator-1.ppt (Size: 445.5 KB / Downloads: 149)
Voltage Regulator
Zener diode is a voltage regulator device because it is able to fix the output voltage at a constant value (DC voltage).
RS is to limit the zener current, IZ so that it is less than the maximum current, IZM (to avoid the zener diode from broken).
Referring to zener I-V charateristic curve, if the voltage across the zener diode zener is between 0-VZ, the zener diode is operating in the reverse bias region, thus it DOES NOT functioned as a regulator.
VTH must at least the same value as VZ (VTH VZ) so that the diode CAN function as a voltage regulator because it is operating in reverse breakdown region.
Zener Diode Regulator
In this simple illustration of zener regulation circuit, the zener diode will “adjust” its impedance based on varying input voltages and loads (RL) to be able to maintain its designated zener voltage.
Zener current will increase or decrease directly with voltage input changes. The zener current will increase or decrease inversely with varying loads. Again, the zener has a finite range of operation.