Peak Electronics DCA75 User Manual page 15

Atlas DCA Pro User Guide
Current Gain (h
DC current gain (h
collector current (less leakage) to the
base current for a particular operating
condition.
The DCA Pro measures h
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 germanium transistors can vary a large amount
with changes in temperature. Even the warmth from your fingers can
alter the gain of a germanium device.
It is quite 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.
)
FE
) is the ratio of the
FE
at a collector
FE
h FE =
(I
Cleak
h FE =167
at I C =5.00mA
Page 15
April 2015 – Rev 1.4
I -I
C Cleak
I B
= leakage
current)
I B
I C =5.0mA