G) Transistors With Special Properties - VOLTCRAFT TT100 Bedienungsanleitung

g) Transistors with special properties

Many modern transistors have special
properties. If the tester has detected
special properties, these functions are
displayed after the OFF/Page button
has been pressed. If no special proper-
ties are detected, the transistor's current
gain appears on the next page. Some
transistors, particularly CRT deflection
transistors and many large Darlington
transistors have a protective diode be-
tween the collector and emitter.
The Philips BU505DF is a typical example of a diode-protected
transistor. Don't forget that the protective diodes are connected
internally between the collector and emitter so that they are nor-
mally reverse biased.
With NPN transistors, the anode of the diode is connected to the
emitter of the transistor emitter.
With PNP transistors, the anode of the diode is connected to the
collector of the transistor.
In addition a lot of Darlington transistors and some non-Darlington
transistors also have a resistor network between the base and
emitter.
The tester can detect the shunt resistor, if it has a resistance of
less than 60 kohm.
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