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Shunt Voltage Stabilizer Circuits |
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Figure 1.
Simple Zener Shunt Stabilizer Circuit Diagram
The circuit
in Figure 1 is a
simple voltage stabilizer circuit that employs a zener diode and a
single resistor. In this circuit, the zener diode, which is the
stabilizing component, is in parallel
(or in shunt) with the load, which is why it is also called a shunt
stabilizing circuit. The value of R must be chosen so that a 'holding
current' of 2 mA will flow into the zener diode even at the lowest input
voltage and maximum load current. The zener diode maintains the
output voltage level by 'conducting' the excess current to ground
whenever the voltage across it becomes excessive.
Figure 2.
Amplified Zener Shunt Stabilizer Circuit Diagram
The circuit
in Figure 2 is another
shunt voltage stabilizer circuit that employs an additional NPN
transistor to the simple circuit in Figure 1. In this circuit, the zener diode
no longer has to conduct large currents to stabilize the output voltage.
The transistor takes care of conducting the excess current whenever the
current required by the load drops. This circuit is also
known as the 'amplified zener' shunt stabilizer.
See
also: Series
Voltage
Stabilizers
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