Heathkit IG-18 User Manual

APPLICA TIONS
SINE WAVE TESTING
Gain and distortion checks are probably the most
common types of sine wave tests that you will
make with this Generator. Usually these tests are
performed on an amplifier. In either of these
tests, a single amplifier stage may be tested
separately, or the entire amplifier may be tested.
Figure 7 shows typical connections for testing a
single stage or a complete amplifier. The output
from the Generator may be connected directly to
the input of the amplifier being tested. If
dance matching is deSirable, you can I"'nl,.,t1"nt't
the matching pads described on Page 48. When
connecting the Signal directly to the input
circuit of a transistor or a tube, use a coupling
capacitor in series with the signal lead to block
any DC voltage that maybe present in the circuit.
®
®
©
To t'est the voltage gain, feed a signal of known
amplitude (voltage) into the amplifier input and
measure the resulting output. The is equal
to the ratio of the output voltage by the
input voltage. This measurement be made
with a voltmeter or an oscilloscope. Fr'eqtuency
response tests +nay be made by the
gain at various frequencies.
the signal from an
amLpljifi€;r can be di::;pl.ayed on an oscilloscope and
comIlaI'ed with the input sine wave from the Sine-
SOllay'e Generator. This test will indicate if dis-
tortion is present and, if so, what kind. Figure 6
shows waveform s of several kinds of distortion.
CD
®
rvwv
rlJ'v
~
W
rvv
N
50
SINE-WAVE LOW BIAS
HIGH BIAS 10%
10%
INPUT SIGNAL
2ND HARMON I C
3RD HARMONIC
APPROX.
20%
DISTORTION
DISTORTION
3RD HARMONIC
DISTORTION
@
® CD CD
®
rvvv
1fL
Vv
'VU
ruu
PRONOUNCED
PRONOUNCED PRONOUNCED
OVERLOADING PRONOUNCED
2ND HARMONIC 3RD HARMONIC
4TH HARMONI C
OF INPUT
OVERLOADING
DISTORTION
DISTORTION
DISTORTION
JUST STARTING DISTORTION
DISTORTION
TYPICAL DISTORTION PATTERNS OBTAINED IN AUDIO AMPLIFIER TESTING
Figure 6

Heathkit IG-18 Specifications

General

Brand	Heathkit
Model	IG-18
Category	Test Equipment
Language	English