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CIRCUIT DESCRIPTION
SVRR (SUPPLY VOLTAGE
REJECTION
RATIO)
SVRR
is the ratio of change of output voltage and change of
supply voltage when
the supply voltage varies.
It is generally used
to indicate the performance of IC.
Change of Output Voltage
SVR
= OO
Change of Supply Voltage
Zener
3 stage
NF
'for
amplifier
RAR
SV
circuit
Bias
circuit
a
R_AMP iP { J07-1540- 0-11)
ae
ped
2.
2.7%
High-frequency
compensation
circuit
ICL. input stage
with FET
Input impedance
resistor
"]
y
¥
+,
—
——
i
{> RENTER ay ES z |
>
i
iff
dl
Zener diode
NF
for SVRR
element
Constant-current
DC PROTECTION
The
DC
potential
at
the
output
terminal
(speaker
terminal)
is always maintained at zero volt by the positive
and negative
power
supply
circuits
and
the differential
amplifier.
However, if a OC potential appears for a certain
reason, the differential amplifier cannot reduce this poten-
tial to zero
volt and
DC current flows into the speaker
load which
is therefore destroyed.
Hence, the DC protec-
tion circuit is installed.
If a DC potential is generated and
Cannot
be compensated
by the differential
amplifier,
the
DC protection circuit actuates a relay to separate the load
(speaker) from the load circuit to protect it against destruc-
tion,
Assume
that there
is a DC
potential
at the output
terminal
and cannot
be compensated
by the differential
amplifier.
Then current begins to flow through Re79 or
Reég0 and Ce29 and Ce30 are charged.
If they are posi-
tively charged,
the base potential rises at Qe29 which
is
therefore turned on. When Qe29 is turned on, the collector
10
=
a
acon
—
TN
il
i
aii
inhi
A
milan
| SEAS
if the supply
voltage
of equalizer
is affected
by the power
amplifier, the dynamic crosstalk, S/N and the dynamic range will be
changed
for the worse.
To resolve these problems,
the dual power
supply is used and SVRR
is set to a high vaiue.
Preventing
High-frequency
rail
DC protection
Rectifier
aeons
diode
potential of Qe29 ts lowered and the bias voltaye of Qe30
and Qe31
is also lowered.
Thus Qe30 and Qe3lare turned
off and the relay separates the load from
the carcuit.
If
Ce29 and Ce30 are negatively charged, the dioces De13 ~
15 are biased in the forward direction
to lowe
the base
potential
of Qe30.
Thus Qe30 and Qe31
are turned off
and the relay also functions to separate the load from the
circuit,
This DC protection circuit is devised to preeant shock
noise which may occur after power switch is on, When the
power
supply
circuit
is switched
on, +Vcc
cureent
flows
through
Re82
and Ce31.
The relay remains t
separate
the load until Ce31
is charged up, since the bas: potential
at Qe30 is not raised.
When Ce31 is completely
charged,
Qe30 is turned on and the relay is reset.
No s\Ock noise
occurs since this time period (dependent on the time con-
stant of Re82 and Ce31) is longer than the circ t stabitiz-
ing time after power switch is on.
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