Sencore TF151 - Common Transistor Terminology; TF151 Controls Overview; Selection Switches; Calibration and Test Buttons

Gate Leakage (lGSS) measured at VGS = 4V, VOS = 0
One
range 0-100 microamps lower 1/2 of scale
100- 5000 microamps upper 1/2 of scale
Zero Bias Drain Current (lOSS)
Measured at VOS = 5V, VGS = 0
General
Electrical: 105/130 VAC, 50/60 Hertz at 10 watts
Physical:
9 1/2" High x 7 1/2" wide X 6" deep
Weight: 9 pounds
COMMON TRANSISTOR TERMINOLOGY
The terms used in describing transistors, both bi-polar and FET types are fairly
new to the service industry. By knowing the standard format of the terms, such as
ICBO orIGSS, the technician can figure justwhateach term means. The main letters
are I and V and stand for current and voltage. The sub letters are the elements of
the
device and tell between which elements the voltage is applied or the current flows.
The sub letters C, B, and E stand for the collector, base, and emitter of a bipolar
transistor. The term ICBO therefore stands for Current between the collector and
base. The 0 indicates that the third element, the emitter in this case, is left open.
The ICBO is the term used to designate leakage current in the bi - polar transistor.
In the field effect transistors, the term IGSS is the leakage current from the gate to
the
source. The third sub letter indicates that the third element, the drain, is short-
ed to the second element or source. lOSS is refered to as the zero bias drain current.
It is of course current from drain to the source. The third letter indicates the gate
is shorted to [he source for a condition of zero or no bias.
When the third letter is missing from the sub letters such as lOS' then the term
must have a condition listed with it to tell what bias is applied to the gate or under
what conditions the current is flowing.
Knowing
that the subletters indicate the elements in question and that the third letter
when used indicates the condition of the third element, the technician can readily
figure out most of the transistor terms that he will encounter.
CONTROLS ON l1 -IE , TF151 IN - CIRCUIT TRANSISTOR AND FET TESTER
'N' CHAN/NPN - 'P' CHAN/PNP Switch. Selects the proper polarity of voltage applied
to the collector or drain of the transistor under test and is used when checking the
forward and reverse currents of a diode.
Gm ZERO and BETA CAL Control. Is adjusted for each transistor to compensate
for various internal impedance differences found in transistors and insures an ac-
curate beta or Gm reading.
GAIN button. Used only for beta and Gm checks and is not used for leakage measure-
ments.
lOSS Button. Used for the zero bias drain current check and for matChing and pair-
ing of field effect transistors.
BIAS Switch. Selects either NORM bias for depletion type field effect transistors or
POS for the enhancement type field effect transistors.
FUNCTION SWITCH. Selects the proper tests for regular transistors or field effect
transistors.
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