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Current to Voltage converter

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hami1992

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Hello everybody

I have a problem in building current to voltage converter, I want to simulate it first. lets say I have a current value of 40 micro amperes which I want to convert into suitable voltage then what kind of circuit I would build and how can I select the component values of resistors and others if there are any.

Please guide I would be very grateful to all of you.

Thanks
 
I have to get the current value from a photo detector (Position sensitive detector) and then I have to convert it into a suitable voltage to be fed into DAQ 6009 for Lab view.
 
Current to voltage conversion may be done using a single resistor. Use Ohms law, V = IR

You could also use a transresistance amplifier; the feedback resistor is the same value as above. One of the simplest uses a single opamp, with a resistor in the negative feedback path, the input current connected to the inverting input, the noninverting input goes to the reference. Note that this will have negative gain, but can of course be inverted with another amp.
 
Thanks dougy but I came to know that such kind of circuit may produce more noise and its better to use a T network for the feedback path, so what do you think and if I use a T network then how would I adjust the resistor values?
 
You adjust the values of the T-network resistors so that the desired Op Amp output voltage applied to the input side of the network will give a current of 40 micro amps through the output network resistor with the resistor connected to ground.
 
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Thanks dougy but I came to know that such kind of circuit may produce more noise and its better to use a T network for the feedback path, so what do you think and if I use a T network then how would I adjust the resistor values?

See **broken link removed** under the complex feedback section

I'm not sure a T feedback network is useful here. For a gain giving 5V out from 40uA in, the feedback resistance w/o the T network is 125k, which is not particularly large.
 
I-V conversion using a single resistor is just fine in that range. The closer the I-V converter is to your detector, the better although proper shielding should be fine. At those levels, you don't really need to concern yourself with guarding.

Vos is an important parameter for I-V converters and so is limiting the BW with a cap across the FB resistor. Using an OP amp that is unity gain stable will also help.
 
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