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

BD140-16 Medium Power PNP TransistorBD140-16 PNP
          Medium Power Bipolar Transistor High Gain version

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