TM 11-6625-539-15-2
the source and the gate is picked off at the junction of
5-8. F.E.T. READ Check
R17 and R18 and is applied to the input of audio
GM measurements of field effect transistors are ac-
amplifier Q4, Q5, and Q6. The output of the audio
complished by the test set in the following manner.
amplifier is rectified by bridge CR1, CR2, CR3, and
The 1-kHz multivibrator, when properly calibrated
CR4 and is applied to the meter. A full scale meter
by adjustment of CAL potentiometer R5, applies a
reading indicates that tile square wave applied to the
symmetrical 100-mv square wave between the source
F.E.T. is 100 mv in amplitude. The output level of
and gate of the test device. Operating voltages are
the multivihmtor (input level to the test device)
also applied to the test device. The 1-kHz square wave
is varied by adjusting CAL potentiometer R5. The
appearing at the drain of the test device is applied
signal level applied to the test device can be accu-
to the input of the audio amplifier. The output of the
rately set at 100 mv by adjustment of CAL potentiom-
audio amplifier is rectified by bridge CR1, CR2, CR3,
eter R5 while observing the meter for a full scale
and CR4 and is applied to the meter. The meter is
calibrated directly in GM micromhos.
reading.
