Characteristics of a Junction Diode

A diode's behaviour is summarised experimentally by plotting the current through it against the voltage across it -- separately for forward bias (9.3.3.1) and reverse bias (9.3.3.2) -- since the two regimes differ by several orders of magnitude in both current scale (mA versus $\mu$A) and shape. Both curves are obtained from essentially the same basic test circuit -- a diode, a current-limiting resistor, a variable DC supply, and meters to read the voltage across and current through the diode -- with only the diode's orientation (and hence its bias direction) and the meter ranges (milliamps for forward current, the far smaller microamps for reverse current) changed between the two tests. Comparing the two characteristics side by side is itself instructive: the forward branch is steep and rises quickly past the knee voltage, while the reverse branch stays almost flat at a tiny leakage current right up until …