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photodiode using opamp output problem

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hiren.dave@bhuved.com

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HI,

i am using photodiode with opamp as a photoconducting method. I am getting output well but output contains pulses. I can't understand that why photodiode and amplifier is generating pulses. help me to solve this problem. i am attaching circuit and dso output herewith.

circuit.JPGpulse ch1 is point c and ch2 is point a.jpg
 

For reproducable operation, there must be a resistor from OP output to non-inverting input (to form a I/V converter or transconductance amplifier).

It's unlikely that LM324 outputs the shown pulses, these are rather interferences picked up from the enviroment.
 
why have you connected opamp in open loop this way , it works as a comparator rather than amplifier as gain of this opamp circuit is not defined !!!
 
thanks for replying me.

If i connect feedback of 5.6 Kohm , no change in output pulses. output voltage is significantly decreases. photodiode itself giving pulsating output.
 
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    hd.

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no change in output pulses
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Either if the pulses are actually present in the photo current, only at the OP output (is it really a LM324?) or picked up by your oscilloscope ground clip somehow, they are apparently real.
 

You are using single rail power and the inverting input! Shouldn't you use the non-inverting input and apply some feedback.
 

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