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.
