CXA2555Q
RF DC Amplifier
The signal currents from the photodiodes A, B, C and D are I-V converted and input to Pins 3 and 4 as PD1 =
A + C, PD2 = B + D.
These signals are added by the RF summing amplifier, inverted by the RF drive amplifier and output to Pin 32.
The VCA control voltage on Pin 28 is used for the gain adjustment.
47k
Vc
RF C
SUM OUT
30
RFO
32
28
10k
I-V
I-V
20k
20k
PD1
PD2
3
4
VCA
Vc
RF
Summing Amp
The low frequency component of the RFO output voltage is as follows:
VRFO = 4.9 × (PD1 + PD2)
(RFC voltage = 1/2 VC)
Focus Error Amplifier
The operation of PD2-PD1 is performed and the resulting signal is output to Pin 15.
27p
174k
I-V
16k
16k
FE
15
PD1
PD2
3
4
Focus
Error Amp
I-V
164k
87k
Vc
27p
14
FE B
47k
The low frequency component of the FE output voltage is as follows:
174k
VFE =
× (PD2 – PD1)
16k
= 10.9 × (PD2 – PD1)
– 15 –
SONY [ SONY CORPORATION ]
