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A GREAT ER M EA SU R E O F C O N F I D E N C E probe pads that connect to more than one
device under test (DUT). The most frequent
application for common pads is to connect
the source terminals together for a set of
transistors (Figure 1).
However, connection of multiple DUTs to
one probe pad can require substantial lengths
of metal line between the DUTs, resulting
in substantial parasitic resistances. In turn,
currents flowing through the metal line can
introduce substantial voltage drops.
In Figure 1, R1, R2, and R3 represent
parasitic resistances and voltage drops in the
line connecting the common source pad to
Test Structure Design
the transistor source terminals: