Velleman DCA75 User Manual
Page 19
Atlas DCA Pro User Guide
December 2012 – Rev 1
Page 19
Free Wheeling Diode
Some transistors, particularly CRT deflection transistors and many large
Darlingtons have a protection diode (“free wheeling diode” or “body diode”)
inside their package connected between the collector and emitter.
If a free-wheeling diode has been detected, it is shown on the schematic
symbol. Some examples are shown here:
The Philips BU505DF is a typical example of a diode protected bipolar
transistor. Remember that the diode (if present) is always internally connected
between the collector and the emitter so that it is normally
reverse biased.
For NPN transistors, the anode of the diode is connected to
the emitter of the transistor. For PNP transistors, the anode
of the diode is connected to the collector of the transistor.
PNP Silicon BJT
Red-B Green-C Blue-E
HFE=61