3.3
Diode
The control settings for a typical diode measurement, and the results of that measurement, are shown in figure 4.
(a) Control Settings
(b) Result
Figure 4: Diode
A diode VI characteristic could be measured by placing a voltage between its terminals and measuring the
current (voltage-driven), or passing a current through it and measuring the terminal voltage (current-driven).
Either one will work, but current increases very rapidly with voltage once the voltage exceeds the threshold for a
diode. Conversely, forward voltage increases very slowly with current, so a current-driven measurement is more
controllable and precise.
The current source/sink is available at the centre (Blue) terminal. For the Diode measurement, the software
selects sourcing of current from that terminal. The left (Red) terminal acts as a constant voltage source for return
for the current.
3.4
Zener Diode
The zener diode should be measured using the
Diode
measurement configuration, which is current-controlled.
Figure 5 shows the characteristics of a 1N3022 zener diode. Figure 5(a) is the forward characteristic, which
is similar to the forward characteristic of any silicon diode.
Figure 5(b) shows the reverse characteristic. The inverse of the slope of this characteristic is the zener in-
cremental resistance. The 1N3022 is billed as a 12 volt zener. The measurement shows it is more like 10 volts,
highlighing the importance of a curve tracer measurement to verify a device characteristic.
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