I to V Conversion w/ Photodiode & IV Converter

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In summary: It's not a limit you should try to stay under. You can if you want but its not a problem if you don't.In summary, the conversation discusses the use of a photodiode and opamp in a circuit to convert micro amps to nano amps without damaging the opamp. The experts suggest using an opamp in the classical I-V converter arrangement and explain that the current entering the inverting terminal can be neglected. They also provide a circuit schematic and a link to a helpful video on opamps. The conversation ends with a clarification on the input bias current parameter of opamps.
  • #1
Dheeraj12
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Hi all,
I need to convert i to v using photodiode and iv converter, now the photodiode can give reverse light current upto micro amps and to convert it to volt i am using opamp with has max input bias current of about nano amps , now how can i convert this micro amps to nano amps because it should not destroy my opamp , can you please suggest a current limiter circuit so that my voltage remains the same
 
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  • #2
I am afraid, you are confused regarding the currents.
It is the INPUT current into the opamp which is in the nano-ampere range.
Hower, this can be neglected using an opamp in the classical I-V converter arrangement.
Do you know how such a circuit (with feedback) looks like?
 
  • #3
Y
Yeah, but i am using an inverting ckt theonly issue is regarding e currentthat into the inv terminal , will current in microamps damage the opamp
 
  • #4
No - the current enters the feedback resistor.
 
  • #5
Oh thanks... Just got that thanks.. Thank you sir
 
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  • #6
Ok so the current goes via feedback and maintains a voltage level vo and keeps non inv at thesame level... So it does not goto inverting terminal... Right,, sir
 
  • #7
Can I suggest you post your circuit diagram.
 
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  • #8
I agree with CWatters, it's awkward to give a useful answer without knowing which components you are using and where they sit in your circuit.

I think, if you are using an appropriate op-amp for your purpose, the bigger concern would be in handling noise to get a useful response from your monitor.
 
  • #9
IMG_20160207_212937942.jpg
 
  • #10
Please find the circuit attached above
 
  • #11
Dheeraj12 said:
Hi all,
I need to convert i to v using photodiode and iv converter, now the photodiode can give reverse light current upto micro amps and to convert it to volt i am using opamp with has max input bias current of about nano amps , now how can i convert this micro amps to nano amps because it should not destroy my opamp , can you please suggest a current limiter circuit so that my voltage remains the same
The circuit schematic you posted does not use a photodiode...
 
  • #12
berkeman said:
The circuit schematic you posted does not use a photodiode...
Well i used an ldristead of photodiode to illustrate that, since my simulator didnt have the phtodiode
 
  • #13
Dheeraj12 said:
Well i used an ldristead of photodiode to illustrate that, since my simulator didnt have the phtodiode
That's a completely different circuit than the one you were asking about. Just find an example circuit using Google Images and post that instead so we can discuss it. :smile:
 
  • #15
Thank you sir
 
  • #16
Dheeraj12 said:
Thank you sir
You are welcome, but you didn't answer my question. I understand that the language translation issue is a problem, but we should still be able to help you if you would ask a clear question based on that simplified schematic. :smile:
 
  • #17
You can also use the schematic berkeman posted with an LED however the output will likely be lower than a purpose built photodiode. Single supply operation is possible if you apply an appropriate voltage to the non-inverting input.

BoB
 
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  • #18
Well,my issue was the current entering into the the inverting terminal of opamp exceeding the specified limit, but later on found out that most of the current went thro the feedback R , and the current entering invl was only nano amps
 
  • #19
For voltage feedback op amps you don't want to rely on the exact value of the input bias current as this is a parasitic. You want to design your circuit so that the bias current is either insignificant or you compensate for it somehow.

BoB
 
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  • #20
Dheeraj12 said:
Well,my issue was the current entering into the the inverting terminal of opamp exceeding the specified limit, but later on found out that most of the current went thro the feedback R , and the current entering invl was only nano amps

That's correct, you have discovered a main rule of Op-Amp circuits
In an ideal/near idea situation no current flows into or out of the inputs of an op-amp

have a look at this great video from Dave @ EEV-blog

http://www.bing.com/videos/search?q...950D0C45487CFCBDAEFE950D0C45487CFC&FORM=VIRE1I have posted this link a number of times over the years :smile:
cheers
Dave
 
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  • #21
Dheeraj12 said:
Well,my issue was the current entering into the the inverting terminal of opamp exceeding the specified limit,

I think you misunderstand this parameter. Its not a limit you must comply with. Its a limit that the manufacturer of the op amp has designed it to achieve. Eg the op amp is guaranteed not to let more than this much current flow into the inputs.
 
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FAQ: I to V Conversion w/ Photodiode & IV Converter

What is "I to V Conversion w/ Photodiode & IV Converter"?

"I to V Conversion w/ Photodiode & IV Converter" is a process used in scientific experiments to convert the current (I) output of a photodiode, which is a type of light sensor, into a voltage (V) output. This voltage output is then measured using an IV converter, which is a device that converts the voltage into a digital signal that can be read and analyzed by a computer or other device.

How does "I to V Conversion w/ Photodiode & IV Converter" work?

First, the current output from the photodiode is passed through a resistor, which converts the current into a proportional voltage. This voltage is then amplified and filtered by the IV converter, which outputs a clean and accurate voltage signal that can be measured and recorded.

Why is "I to V Conversion w/ Photodiode & IV Converter" important in scientific experiments?

"I to V Conversion w/ Photodiode & IV Converter" is important because it allows scientists to accurately measure and record the output of photodiodes, which are commonly used in experiments to measure light levels or detect changes in light intensity. By converting the current output into a voltage, the signal can be easily read and analyzed by computers or other devices, making it an essential tool in many scientific studies.

What are some common applications of "I to V Conversion w/ Photodiode & IV Converter"?

"I to V Conversion w/ Photodiode & IV Converter" is commonly used in experiments involving light measurements, such as in the fields of astronomy, environmental science, and materials science. It is also used in the development of electronic devices that utilize light sensors, such as cameras and solar panels.

Are there any limitations or considerations when using "I to V Conversion w/ Photodiode & IV Converter"?

One limitation of "I to V Conversion w/ Photodiode & IV Converter" is that it is only accurate for low frequency signals. For high frequency signals, the capacitance of the photodiode and other components can affect the accuracy of the conversion. Additionally, it is important to choose the appropriate resistor and IV converter for the specific photodiode being used in order to ensure accurate and reliable measurements.

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