– 10 –

CXA2525AM/AN

Note on Operation

The RF AC maximum output amplitude is 1.3 Vpp when Pin 13 and 14 are capacitor-coupled shown in

Application Circuit.

Description of Operation

RF Amplifier

The signal currents from the photodiodes A, B, C and D are I-V converted, and input to Pins 3, 4, 5 and 6.

These signals are added at the RF summing amplifier and inverted at the RF drive amplifier and then output to

Pin 14.

The low frequency component of RFO output voltage is as follows:

×

× (A + B + C + D)

= 2.45

× (A + B + C + D)

Focus Error Amplifier

The operation of (B + D) – (A + C) is performed and the resulting signal is output to Pin 12.

The low frequency component of FE output voltage is as follows:

× (B + D – A – C)

= 5.43

× (B + D – A + C)

A

B

C

D

I-V

I-V

I-V

I-V

10k

10k

10k

10k

10k

2k

RFO

RF Drive Amp

VC

RF

Summing Amp

VC

RF_ M

3

4

5

6

17

14

1k

16

3.9k

390

4.9k

1p

13p

68p

15

LPF_SW

BPF_SW

10k

10k

4.9k

2k

A

B

C

D

I-V

I-V

I-V

I-V

64k

64k

64k

64k

348k

Focus

Error Amp

348k

15P

FE

15P

VC

174k

3

4

5

6

12

348k

64k