TINA/Spice/OPA857: OPA857

harini burra

Prodigy 120 points

Part Number: OPA857
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hello,

i have question related to the OPA857 functioning, i want to know how the voltage swing is set to 0.6V to 1.9V.

because the input to the OPA857 is a current source.

can i know how the input current is changing into the output voltage swing . are there any calculation or any formula for the conversion

thank you

over 6 years ago

0 Karan Kotadia over 6 years ago

TI__Genius 16735 points

Hi,

The following articles should help you with understanding the workings of the TIA's

www.analogictips.com/.../
www.electronicdesign.com/.../whats-all-transimpedance-amplifier-stuff-anyhow-part-1
www.tij.co.jp/.../snoa942a.pdf

If you have specific questions regarding any of these please let me know.

Thanks!
-Karan

0 harini burra over 6 years ago in reply to Karan Kotadia

Prodigy 120 points

hi,

thank you for the response

my question is how the output voltage is changing with the input current applied

from the formulae vout= -R*I for calculating voltage for the applied current of 100nA and for a resistor of 5kohm the output voltage should be 0.0005V but why does OPA857 swings from 1.83V to ground

does input current from the photodiode does not have any effect on the output voltage??

0 Karan Kotadia over 6 years ago in reply to harini burra

TI__Genius 16735 points

Hi Harini,

Do you have a constant current source? The output voltage will only swing when the input current changes. As you mentioned the output voltage has a direct relation to the input current. Photodiodes convert light into current, which a transimpedance amplifier then converts to voltage.

Thanks!
-Karan

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TINA/Spice/OPA857: OPA857