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1) Focus error amplifier unit
This focus error amplifier outputs photodetector output
(A + C) or (B + D) from pin 16 of IC201 (TA2150FN) via a
differential amplifier and an error amplifier assuming
(A + C - B -C) as an FE signal. The low frequency
component of voltage FE is expressed as
FE = (A + C - B - D) × (150 k / 62 k) × (60 k / 60 k) × (12 k /
60 k) = 4.84 times.
An S curve of approximately 1.45 Vpp is obtained in the
FE output on the basis of Vref. The cutoff frequency is
26 kHz or 133 kHz.
Fig.2:FE CIRCUIT
2) Tracking error amplifier unit
This tracking error amplifier unit outputs photodetector
output E or F from pin 14 of IC201 (TA2150FN)via an
amplifier and an error amplifier assuming (E - F) as a TE
signal. The low frequency component of voltage TE is
expressed as
TE = (E - F) × 300 k / 100 k × 155 k / 328 k × 82 k / 20 k =
5.8 times.
A TE waveform of approximately 1.51 Vpp is obtained
in the TE output on the basis of Vref. The cutoff
frequency is 44.5 kHz or 29.4 kHz.
Fig.3:TE CIRCUIT
CX-961
3
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