CXA1782CQ/CR
Tracking Error Amplifier
The photo diode currents input to E and F pins are each current-voltage converted by the E I-V and F I-V
amplifiers.
1k
RF1
3.3µ
260k
12p
TE AMP
F
30k
96k
VF
38
→
iF
30k
F I-V AMP
VC
42
TEO
VC
RE1
VC
260k
12p
E
VE
39
→
iE
VC
E I-V AMP
VC
VC
40
EI
The CXA1782 tracking block has built-in circuits for balance and gain adjustments to enable software-based
automatic adjustment.
The balance adjustment is performed by varying the combined resistance value of the T-configured feedback
resistance at E I-V AMP.
RF1 x RF2
F I-V AMP feedback resistance = RF1 + RF2 +
E I-V AMP feedback resistance = RE1 + RE2 +
= 403kΩ
RF3
RE1 x RE2
RE3
Vary the value of RE3 in the formula above by using the balance adjustment switches (BAL1 to BAL3).
For the gain adjustment, the TE AMP output is resistance-divided by the gain adjustment switches (TOG1 to
TOG3), and it is output at Pin 42.
These balance and gain adjustment switches are controlled through software commands.
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ETC [ ETC ]
