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5. Special Circuit Descriptions
5-1 RF Amp Block


5-1-1 RF Amplifier
The two currents from input pins PD1 (A+C) and PD2 (B+D) are converted into voltages through I/V Amp,
and they are added to RF summing Amp. The photo diode (A+B+C+D) signal which is I-V changed is
outputted by RFO (pin74). At this pin, the eye pattern can be checked.




58K


PD1 65 - VA 10K
-
+ 74 RFO
IV AMP
+
VC RF SUMMINGAMP
VC
58K


PD2 66 -
VB 10K
73 RF-
+
IV AMP
VC




5-1-2 Focus Error Amp
The output of the focus error amp is the difference between RF I-V AMP(1) output Va and RF I-V AMP(2)
output Vb,just is the Photo Diode ((A+C) - (B+D)) signal which is I-V changed.
The focus error bias voltage applied to the (+) of focus error amp can be changed by D/A converter as shown in
diagram, so that the offset of focus error amp can be adjust automatical.
Focus error bias can be adjusted from the range of +100mV ~ -100mV by connectiong the resistor with pin 63
(FEBIAS).




164K

32K
VB> -
32K 59 FE1
VA> +
sev-stopb
160K
SW1
FEBIAS 63
sev-stop
<5 Bit Counter> 4K

3K -
fcmpo
X1 X2 X4 X8 X16
+
-

+ FEBIAS VC fe-stopb




Samsung Electronics 5-1
Special Circuit Descriptions




5-1-3 Tracking Error Amp
The current signals from the side spot photo diode (E and F) are input to the E and F pin and converted into
voltage signals by E I-V and F I-V AMP. The output of tracking error amp is due to the difference between
E I-V AMP voltage output.
The E-F balance can be adjusted by modifying the gain of E I-V AMP, and the tracking gain(Pin TE1) can be
adjusted automatically by micom program.



TE1 LPFT

54 55



F 67 IV AMP - BALL
- WIN COMP
68 IV AMP + BALH
E
TGFI GAIN-UP/DOWN To ISTAT,TRCNT
TGL
EI 79 WIN COMP
7.5K

3.3K


1.5K
16K
13K




TGH
56K

27K


13K
220K

110K
75K




BAL< 4 0 >
GAIN< 3 : 0 >
from Digital




5-1-4 Focus OK Circuit

Extracting the DC part of RFI and RFO and comparing with the basic DC level, if RF Level is more than basic
level, the FOK is output. The focus OK circuit generates a timing window of focus on to monitor the focus
search status of focus serve.




40K

40K
74 - 57K
-
75 + 40 FOK
40K +
90K



VC+0.625V




5-2 Samsung Electronics
Special Circuit Descriptions




5-1-5 Mirror Circuit
After RFI signal is amplified by mirror amp, mirror signal is held in peak and bottom circuit. The following of
100KHZ traverse is possible in peak hold circuit and the loss of track count due to defect is counted in bottom
hold circuit. Mirror output beyond 2KHz is.