6-
10
Zener Diodes
Normal switching and signal diodes conduct when forward biased only. When reverse biased,
they act as opens unless they are operated outside design limits. If this condition occurs then so
much voltage is applied that they break down and can no longer prevent current flow.
A zener diode is a different type of diode and is designed for operation when reverse biased
(diode's cathode connected to positive and anode to negative), but under carefully controlled
conditions. When the zener diode is forward biased (diode's cathode connected to negative and
anode connected to positive), they act as regular diodes and begin to conduct at approximately
0.6V.
When reverse biased, it acts as an open circuit until the applied voltage reaches it’s specified
zener voltage, at which time the zener diode begins to conduct current. Even if the reverse
voltage is increased, the voltage across the zener remains constant. This characteristic of a
zener diode allows it to be used as a voltage regulator and reference. The zener diode conducts
in both directions, resulting in it’s Tracker signature having two knees, one at 0.6V and the other
at the zener voltage of the diode. In TSA terminology, this two knee signature is known as the
classic "chair" pattern that is common in many solid state semiconductor components.
Figure 6-16. Tracker Core Circuit Block Diagram with a Zener Diode.
To Next Page
Loading...
