30 WATT POWER
AMPLIFIER
MODULE
This Amplifier is formed by two (2)
stages. The first
stage is a
differential voltage
amplifier,
and
the
second stage is a
voltage and power amplifier
of the
symmetrical inverted darlington
type.
A
differential
amplifier
(Operational Amplifier!
used for the
input circuit keeps
the output at D.C.
ground by
compensating the bias
of the output
transistors.
This circuit makes
symmetry-comple-
mentary output
practical by
eliminating the bias
problems. I.C. 1
is biased equally to
ground
with
R2
and R4.
Since the load is
connected' to Pin 2
of
I.C. 1 through R4,
ground
potential is achieved at
the load.
The I.C. feedback
path from the load
to
Pin
2
of
I.C. 1 also
presents
a
convenient
way to
apply
A.C.
feedback. The amount of feedback is controlled by
R3 and R4 and their ratio determines the
overall
gain of the
amplifier. The very high open loop gain,
which permits
the large negative feedback, is due to
I.C. 1
which operates class
A
with D.C. to
high
frequency.
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