Harman Kardon FL8385 Service Manual page 19

FL8385
APC
1
PD
The laser diode has large negative temperature characteristic in its optical output when
driven with a constant current on laser diode. Therefore, the output on processing monitor
photo diode, must be a controlled current for getting regular output power, thus the APC
(Auto Power Control) circuit is composed.
Reference Power Supply
V
CC1
R
R
R/2
A reference power supply for servo is built-in. The current capacity of the reference supply
is about 3 mA.
V = 1/2 V
REF1 CC1
V = 1/2 V
REF2 CC2
where V = 5 V and V
CC1
19
2
170mV
V
CC2
R
V
20
REF1
R
= 2.5 V
= 1.65 V
= 3.3 V
CC2
LDON
V
CC1
C33
R18
Q1
LD
V
22
REF2
R/2
19
harman/kardon
LASER UNIT
FL8380