JVC AX-Z1010TN User Manual

AX-Z1010TI
Description of Major ICs
@ TORX172 (J101): Optical Receiving Module
(1) Circuit Configuration
Optical
Digital
Input
) a SND (4) no
—|> 3) Vec
Amplification circuit
GND
Comparator
Output
—_
Reference voltage
generation circuit
Peak hold circuit
(2) Circuit Description
When
an
optical
is
input
to
the
Si-PIN
photodiode,
a
current
flows
with
a
sensitivity
of
0.3
A/W
(xp=
650
[nm])
or
less.
This
current
is
impedance-converted
and
amplified
by
the
amplifier
circuit,
and
the
resulting
signal
voltage
is input to the comparator.
On
the
other
hand,
the
reference
voltage
of
the
comparator
is
given
by
the
ATC
(Automatic
Threshold
Control)
circuit.
The
ATC
circuit
is
made
up
of
a
peak
hold
circuit
which
detects
the
peak
value
of
the
input
voltage
and
holds
this
peak
value
for
a
certain
period.
The
period
during
which
the
peak
value
is
held
is
known
as
the
‘‘time
cons-
tant’. It is se to 1—3 usec in case of ‘Toslink’.
The
signal
voltage
from
the
amplifier
circuit
is
divided
in
two
by
a
resistor
and
is
input
to
the
peak
hold
circuit.
Thus,
the
comparator
performs
a
comparison
between
the
output
voltage
of
the
amplifier
circuit
and
the
peak
value that is 1/2 the output voltage.
By
virtue
of
this,
the
comparator
output
can
accurately
reproduce
the
signal
transmitted
from
the
optical
transmis-
sion
module
of
the
transmitter
at
any
time,
even
when
the
optical!
input
varies.
Moreover,
since
the
reference
voltage
generation
circuit
is
provided
to
keep
the
output
voltage
at
the
same
level
as
the
voltage
output
of
the
amplifier
circuit
when
there
is
no
optical
input,
so
that
the
reference
voltage
varies
according
to
the
temperature
drift
in
the
amplifier
circuit
to
minimize
the
change
in
property
due
to
the
tempera-
ture variation.
In
addition,
a
constant
current
power
supply
is
provided
and
the
reference
voltage
of
the
comparator
is
set
slightly
higher
than
the
output
voltage
of
the
reference
voltage
generation
circuit
so
that
the
transmission
is
made
ac-
curately
even
under
the
condition
that
there
is
no
optical
input
for
a
long
period.
(No, 20115} 1-23

JVC AX-Z1010TN Specifications

General

Brand	JVC
Model	AX-Z1010TN
Category	Amplifier
Language	English