BD140-16
Medium Power PNP Transistor
This is a BD140
PNP transistor that can withstand about 80V (Vce) when switched
off and carry 1 Amp collector current (Ic) when on, though it is
running out of gain (Hfe) at that collector current level, as you
can see if you look at the chart of collector current versus gain
in the data sheet linked below. This particular -16 version
denotes the highest available gain grouping and that is definitely
recommended in this design if you are planning to drive currents
any higher than 100mA. This version also has a fully
insulated TO-126 package with no metal area at the back.
This simplifies mounting when you want to bolt it to a heatsink to
cool it down when used in higher power situations. The metal area
on the non-insulated version is usually connected to the collector
internally and bolting it to an instrument case would short it to
ground unless an insulating kit is used. The 'front' is
designated by having the part number scribed onto it and the lead
designations are as shown.
Fairchild BD140-16 Data Sheet
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19-DEC-2025: self canonicalised, direct refs