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8

R03

LIA120

Photodiode

The bandwidth through the part will be:

Where:

P

compensation of the 431.

CTR is the current transfer ratio of the feedback

optocoupler (0.001-0.003).

R

resistor and the LED resistance (25 ohms) and Gm is

the transconductance of the 431 (3 Siemens).

However, since some of these elements vary over

operating conditions and temperature, the bandwidth

should be practically limited to less than 40kHz to

avoid oscillations, which is the value computed by

100pF.

Gm CTR

FB

R

1

R

2

LED

C

1

P

1

< BW Hz

MAX

The output of the LIA120 is a photodiode capable or

withstanding high voltages. For the most accurate

results, attempt to bias the voltage across the cathode

anode the same as V

placed in series with the cathode or anode for desired

output polarity.