BGW 150 - Output Stage and Heat Sink Design; Internal Circuitry Overview

01530-2
All
of
the
semiconductors
in the output
area
are
in
intimate
contact
with the heat
sink.
The bias circuit
is also
mounted
on this isotherm
to
provide
rock steady
bias
stability
with
temperature.
The
voltage
gain circuits
are aiso
mounted
on the
same circuit
board.
A true
operational
amplifier integrated
circuit
acts as the
front end.
The
op-amp is
a special unit
featuring very
low noise, high
speed
(10MHz). The
op-
amp stage
is followed
by a
discrete complementary
pair
acting as an
active current
source/sink and
providing
voltage
gain. The
current
source
is the
ideal way to
drive
the
output
stage, which
is basically a triple
Darlington
voltage follower.
This
sophisticated
circuit
design
makes for an
extremely
accurate
amplifier. The
accuracy
of
an
amplifier
is a function
of the ratio
of the
open
loop
gain
to the
closed loop
gain.
In this
case, the open
loop
gain is
about
1,000,000.
This
extremely accurate
signal processing
enables the
amplifier
to drive
speakers at
very
high
levels while
adding
absolutely
no coloration
of its
own. Even
at
milliwatt
levels, the
output waveform
exhibits
no sign
of crossover
distortion.