Pll Circuit; Power Supply Circuits - Icom IC-2GA Service Manual

(4)
VCO
CIRCUIT (RF UNIT)
D701 changes
the inductive reactance of the
oscillator
(Q702), shifting
the receive
and
transmit frequencies.
Varactor diode
D702
provides frequency
control.
Q703
buffer amplifies
the
VCO
output signal;
Q701
buffer
ampli-
fies
the
PLL feedback
signal.
(5)
UNLOCK SENSOR
CIRCUIT
When
the
PLL
circuit
is
unlocked, pin
7 of IC2
is
"LOW"
and
a
"LOW"
signal
is
applied
to
the unlock
sensor
(023).
The
unlock sensor outputs
a
current amplified
"LOW"
signal to
the
CPU,
IC503
(pin 60).
DATA
CK
PLL
STLB
4
-
4
POWER
SUPPLY
CIRCUITS
(1)
VOLTAGE
LINES
DESC8IFT10N
..
..
Vcc
Battery pack output that
passes through the
power
switch.
Vcc
is
applied to the
power
module
(iC3),
the
AF power
amp
regulator,
and
the following 5
V
lines.
+5
Common
5
V
current-amplified at (Q207,
Q208)
using
1C
output as a reference voltage.
The
heat factor of
the voltage
at
Q207
(Vbe)
equals
that of
the junction voltage
at
Q208.
The
output
is
stable
even with regard to
tempera-
ture
changes.
+5S
Common
5
V
controlled
by
the
power
save
function.
Current-amplified
at
Q213, Q214.
R+5
5
V
controlled
by
the
power
save
function.
Current-amplified at
Q211, Q212.
Used by
the
receiver
circuits.
T+5
5
V
current-amplified
at
Q209, Q210.
Used
by
the transmitter
circuits.
(2)
VOLTAGE REGULATOR
CIRCUIT
(MAIN UNIT)
When
the battery voltage
is
5.5—16
V,
the regulator (IC204)
outputs
a
reference voltage
of 5 V.
The
noise
components
are
removed by
the noise
filter
(C220, R213). This
output
is
applied
to
the current amplifier (0207, 0208).
(3)
CPU
POWER
SUPPLY
CIRCUIT (LOGIC UNIT)
When
the
power
is
turned
off,
voltage
from
the
lithium
battery
is
applied
to
the
CPU,
IC501 (pin 52) via
D502.
4-3