  The properties of bipolar junction transistors (BJTs) are known to vary in
terms of their parameters. In this work, an experimental approach, including
pattern recognition concepts and methods such as principal component analysis
(PCA) and linear discriminant analysis (LDA), was used to experimentally
investigate the variation among BJTs belonging to integrated circuits known as
transistor arrays. It was shown that a good deal of the devices variance can be
captured using only two PCA axes. It was also verified that, though
substantially small variation of parameters is observed for BJT from the same
array, larger variation arises between BJTs from distinct arrays, suggesting
the consideration of device characteristics in more critical analog designs. As
a consequence of its supervised nature, LDA was able to provide a substantial
separation of the BJT into clusters, corresponding to each transistor array. In
addition, the LDA mapping into two dimensions revealed a clear relationship
between the considered measurements. Interestingly, a specific mapping
suggested by the PCA, involving the total harmonic distortion variation
expressed in terms of the average voltage gain, yielded an even better
separation between the transistor array clusters.
