7.2 Typical Application

7.2.1 Optical Current Sensing

A common use case for the LOG200 is an optical current sense circuit, using an external photodiode. Figure 7-5

shows an implementation using an InGaAs, PIN photodiode for a λ = 1.31μm application. This design uses ±5V

supplies, and is intended for use with input currents from 10nA to 100µA. Decoupling capacitors are not shown

for brevity. The design can be easily implemented using the LOG200 Evaluation Module board. For additional

information, bench measurements, and examples for interfacing the LOG200 with photodiodes, see the Perform

Accurate Optical Power Measurements With The LOG200 application note.

100

To Oscilloscope

Photodiode

+

–

+

–

+

–

I2

I1

PD

Bias

IBIAS

VCM

+

–

REFGND

+

–

2.5V

1.65V

REF25

REF165

+

–

REFA

OUTA

OUTB

–IN

+IN

VS+

VS–

VS+

1μA

IREF

I2

I1

2.5V

2.5V

5V

5V

LOG200

–5V

Figure 7-5. LOG200 Optical Current-Sensing Application

LOG200

SBOSA28A – AUGUST 2023 – REVISED DECEMBER 2024

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