Atlas DCA User Guide
October 2007 – Rev 7
Pressing the scroll-off button will result in the transistor’s pinout being
displayed.
Here, the instrument has identified that
the Base is connected to the Red test
clip, the Collector is connected to the
Green test clip and the Emitter is
connected to the Blue test clip.
RED GREEN BLUE
Base Coll Emit
Transistor Special Features
Many modern transistors contain additional special features. If the Atlas DCA
has detected any special features, then the details of these features are
displayed next after pressing the scroll-off button. If there are no special
features detected then the next screen will be the transistor’s current gain.
Some transistors, particularly CRT
deflection transistors and many large
Diode protection
between C-E
Darlingtons have
a protection diode
inside their package connected between
the collector and emitter.
The Philips BU505DF is a typical example of a diode protected bipolar
transistor. Remember that protection diodes are always internally connected
between the collector and the emitter so that they are
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.
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