TM 11-6625-539-14-3
TRANSISTOR CHARACTERISTIC DATA FOR TEST SET,
TRANSISTOR TS-1836C/U
Two of the most important parameters for testing transistors in circuit are I CO and beta. Minimum
value of beta and maximum value of ICO are presented as an aid in determining faulty transistors and
transistors that have started to degrade. Beta normally is specified by the manufacturer at various
collector-to-emitter voltage; however, beta is normally independent of collector-to-emitter voltage
above the saturation voltage. The magnitude of the beta of a transistor, therefore, measured at a
potential slightly above the saturation voltage is very close to the magnitude of the beta measured
at some higher potential. The appendix shows data gathered from manufacturers and specification
sheets which accounts for the various potentials for which beta is given. The same reasoning is true
for the ICO parameter if it does not contain a leakage current. A plot of collector current versus collector
voltage of a reverse-biased collector-to-base junction with a negligible amount of leakage current yields
a graph which rises to some current rather quickly and then remains constant with increasing voltage
until the breakdown voltage of the junction is reached. A leakage component across the junction modifies
this curve in an amount depending on the amount of leakage present across the junction. The figure of
6 volts was chosen as one that would give maximum information on the largest amount of transistors
and diodes. A device with a lower breakdown voltage than 6 volts will not be damaged since the power,
when this measurement is made, is limited to less than 5 milliwatts. The most important parameter for
testing field effect transistors either in or out of circuit is the transconductance of the device. The mini-
mum value of the transconductance of the device is presented as an aid in determining faulty field effect
transistors and transistors that have started to degrade. Transconductance normally is specified by the
manufacturer at various drain-to-source voltages and various drain-to-gate voltages. However, a survey
of the field shows that maximum information on the largest number of field effect transistors would be
presented if 6 volts drain-to-source and 0.1 volt drain-to-source were applied to the device under test.
These voltages were chosen as the test points.
