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[SOLVED] Is this transistor working as a amplifier or anything else

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asimkumar

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Hi all

i have found this circuit in a photo diode amplifier, but i cant understand whether it is a amplifier or a current limiter/source. The photo diode acts as the signal source, and output taken to a op amp.
amp2.jpg
amp3.jpg
 

I think the transistor serves as an active load to prevent sudden fluctuations in the input to the Op amp This is my guess cause there is exactly no op drawn from the transistor whereas only the collector feed is given to it
 
asimkumar said:
i cant understand whether it is a amplifier or a current limiter/source.
Click to expand...

Neither - nor. I think it just generates a fix (reverse) bias for the photo-diode.

Such a low parallel resistor (3.9kΩ) spoils the sensitivity of the photo-diode. It might be ok, however, for a high-speed application.

And I don't think the connection left of R153R & R154R is correct.
 

Hello friends, thank u for response, i got it from google with hints from u all, that was a Device invented by Bernard D.H. Tellegen . this is the same man who invented Tellegen theorem

Thank u All
ASIM
 

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