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1
1.1.3 Focus error amplifier
The photo-detector outputs (A + C) and (B + D) are passed through the differential amplifier and the error amplifier, and (A
+ C - B - D) is provided from the pin 135 as the FE signal. The low frequency component of the voltage FE is calculated as
A
below.
FE = (A + C - B - D) x 8.8k / 10k x 111k / 61k x 160k / 72k
= (A + C - B - D) x 3.5
For the FE outputs, an S-shaped curve of 1.5 Vp-p is obtained with the REFO as the reference. The cutoff frequency for
the subsequent stage amplifiers is 14.6 kHz.
1.1.4 RFOK circuit
This circuit generates the RFOK signal, which indicates the timing to close the focus loop and focus-close status during
the play mode, from the pin 70. As for the signal, "H" is output in closing the focus loop and during the play mode.
Additionally, the RFOK becomes "H" even in a non-pit area, since the DC level of the RFO signal is peak-held in the
B
subsequent digital block and compared at a certain threshold level to generate the RFOK signal. Therefore, the focus is
closed even on a mirror-surface area of a disc. This signal is also supplied to the microcomputer via the low-pass filer as
the FOK signal, which is used for protection and gain switching of the RF amplifier.
1.1.5 Tracking error amplifier
The photo-detector outputs E and F are passed through the differential amplifier and the error amplifier to obtain (E - F),
and then provided from the pin 138 as the TE signal. The low frequency component of the voltage TE is calculated as
below.
TEO = (E - F) x 63k / 112k x 160k / 160k x 181k / 45.4k x 160k / 80k
C
= (E - F) x 4.48
For the TE output, TE waveform of about 1.3 Vp-p with the REFO as the reference. The cutoff frequency in the subsequent
is 21.1 kHz.
Pickup Unit
D
P5
P10
VREF
P1
P6
E
Fig.1.1.3 TE
F
6
1
2
CD CORE UNIT
PE5547A
+
-
E
E
11
11
132
112k
+
-
F
F
9
9
131
112k
2
3
TEOFF setup
+
-
45.36k
161k
63k
+
-
45.36k
160k
160k
63k
CX-3195
3
4
TE A/D
+
138
-
160k
80k
137
+
139
-
60k
20k
140
-
VREF
+
Inside TEC
4
TEO
47p
TE-
TE2
10000p
TEC
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