Darlington Transistors - Peak Atlas DCA75 Pro User Manual

Peak Atlas DCA Pro User Guide

Darlington Transistors

If the device is a Darlington transistor (two BJTs connected
together), the unit will display a similar message to this:
lower at the test currents used by the DCA Pro. This is normal and is not a fault
with the transistor or the DCA Pro.
It is important to note that if a Darlington does contain a base-emitter
shunt resistor network, any measurements of current gain (h
very low at the test currents used by the DCA Pro. This is due to the
resistors providing an additional path for the base current. The readings
for gain however can still be used for comparing transistors of a similar
type for the purposes of matching or gain band selecting.
Note that the DCA Pro will determine that the transistor under test is a
Darlington type if the base-emitter voltage drop at 5mA is greater than
1.00V for devices with a base-emitter shunt resistance of greater than
60kΩ or if the base-emitter voltage drop is greater than 0.80V for
devices with a base-emitter shunt resistance of less than 60kΩ.
Darlington devices that do not have
internal resistors can exhibit very high
gain (h ).
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This second example (left) shows the
display for a Darlington transistor that
has internal resistors connected to the
base-emitter connections. This causes
the h measurement to become much
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) will be
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