DDC264 Photodiode input with negative Vbias

Mohd Zulhadi Zainal Abidin

Other Parts Discussed in Thread: DDC264

I currently testing the DDC264 to measure the dark current of few photodiodes (see the schematic above).

The photodiodes are biased with -4V from a single supply. Is there a problem with the my schematic since the measurement I have collected seem to be

gibberish.

Thank you

over 12 years ago

0 Eduardo Bartolome over 12 years ago

TI__Expert 4680 points

If I understand correct, you seem to be applying a bias voltage at the input of the device (through the 100Ohms). That is "fighting" with the internal bias voltage set by the device, close to QGND (see, for instance, diagram on page 10). In page 3, the voltage at the input pin is specified, under DC Bias Voltage (see note 6 too).

Not sure of the overall application, but if what you need is to bias the diodes, probably you should connect their cathodes to the Vbias and anodes to the DDC264 inputs and make Vbias positive.

Best regards,

Edu

0 Mohd Zulhadi Zainal Abidin over 12 years ago in reply to Eduardo Bartolome

Prodigy 80 points

Thanks Edu for the help

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DDC264 Photodiode input with negative Vbias