Peak Atlas DCA Pro
User Guide
June 2019
–
Rev 1.7
Page 15
Current Gain (h
FE
)
DC current gain (h
FE
) is the ratio of the
collector current (less leakage) to the
base current for a particular operating
condition.
The
DCA Pro
measures h
FE
at a collector
current of nominally 5.0mA and a
collector-emitter voltage of between 3V
and 9V.
The gain of all transistors can vary
considerably with collector current,
collector voltage and also temperature.
The displayed value for gain therefore
may not represent the gain experienced
at other collector currents and voltages. This is particularly true for large
devices. The displayed value of gain is very useful however for comparing
transistors of a similar type for the purposes of gain matching or fault finding.
Darlington transistors can have very high gain values and more variation of
gain will be evident as a result of this.
The current gain of transistor (particularly germanium types) can vary a
large amount with changes in temperature. Even the warmth from your
fingers can alter the gain of a device. It
’
s best to let the temperature of
the device stabilise for a minute or two before measuring the gain.
It is normal for transistors of the same type to have a wide range of gain
values. For this reason, transistor circuits are often designed so that their
operation has little dependence on the absolute value of current gain.
