M02011

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14

CMOS Transimpedance Amplifier with AGC

for Fiber Optic Networks up to 622 Mbps

Rev V5

4.2

Monitor Calibration

To achieve the best monitor accuracy, both the slope and calibrated offset should be used. The offset calibration is

achieved by measuring the dark current from the MON output. The calibrated monitor value is usually determined

by y = mx + b or:

Where Slope = 1/Imon_ratio (Table 1-4) = 1/0.7 = 1.43 and

4.3

Selecting the Monitor Resistor

As described earlier the high impedance monitor output sources a replica average photodiode current for

monitoring purposes. If detected by converting the current to a voltage through an external resistor (Figure 4-1),

monitor resistor.

Table 4-1.

Selection of Rm for Maximum Input Current

Optical Power (dBm)

Rm (

Ω)

4

+6

500

2+3

1000

1

0

2000

0.5

–3

4000