Denon PMA-1315R - New Circuit Functions; Bias Control Circuit Characteristics; Bias Control Circuit Block Diagram; Control Circuit Power Supply

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PMA-1315R
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FUNCTION OF NEW CIRCUIT
1. CHARACTERISTIC OF THIS CIRCUIT »
The
junction
temperature
of
power
amplifier
output
transistor
always
varies
by
an
ambient
temperature
and
music
signal.
Occurrence
of
junction
temperature
varying
causes
in
change
of
bias
current,
unstable
function,
thus
pure
music
‘signal
playback
is
unable
io
do.
a
a
nga
To
maintain
fixed
bias
current
and
to
make
pure
music
signal
playback
possible
is
the
purpose
of
this
circuit.
This
circuit
holds
stable
bias
current
condition
within
a
few
seconds
after
tuming
on
the
power.
©
;
6
2.
BLOCK
DIAGRAM
OF
BIAS
CONTROL
CIRCUIT
FUNCTION
As
explained
in
Fig.
1,
detects
a
voltage
across
the
emitter
resistors
(RE)
of
TR1,
TR2.
Converts
the
detected
voltage
and
-
comparing
with
the
reference
voltage
to
make
the
bias
current
value
in
stable
state.
Actually,
these
functions
are
performed
by
1
chip
IC.
:
TAI, TR2: Output transistor
RE : Emitter resistor
Fig. 1
3.
POWER
SUPPLY
FOR
ACTUATING
CONTROL
CIRCUIT
TRI
ro
[-*
>
Talc
(vt)
The
circuit
(IC)
controlling
bias
current
actuates
by
tk Power supply circut _—-‘featting.
RE
Na
ebewe
Output
Accordingly,
the
power
supply
is
also
needed
to
be
, floated.
RE
TRe
in this circuit, as indicated in Fig. 2, output is common
to provide +, ~ power system and supplies to IC.
> Tol (V7)
Fig. 2
10