  Transistors have provided the basis of modern electronics. Being relatively
intricate devices, and often exhibiting intense parameter variation, this type
of electronic devices has motivated much research interest especially regarding
their characterization and modeling. In this work, we apply a recently reported
modeling methodology, based on the Early effect, for characterizing new old
stock NPN and PNP small signal germanium junction transistors and comparing
them to more modern silicon bipolar junction devices. The Early approach is
special in the sense that its two parameters, namely the Early voltage $V_a$
and a proportionality parameter $s$, are fixed and independent of transistor
operation. Remarkable results are obtained, including the fact that the four
considered groups, namely NPN and PNP germanium and silicon devices, occupy
mostly non-overlapping regions in the Early parameter space, with PNP devices
presenting larger parameter variability in both cases. Surprisingly, the
considered germanium devices exhibited smaller parameter variability than
observed for the silicon counterparts. When mapped into the more traditional
space defined by the current gain and output resistance parameters, the four
transistor groups exhibited much larger overlaps and yielded a clustering
structure much less organized than allowed by the Early mapping. This result
suggest that the Early representation of transistors is more compatible and
inherently related to the structure of amplifying devices such as those
considered in this work. In addition, it was verified that the center of mass
of each of the NPN-PNP pairs of germanium and silicon devices are crossed by
respective $\beta$-isolines for gains of 130 and 250, respectively. Germanium
devices were also characterized as having smaller output resistance and smaller
magnitudes of Early voltage.
