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current to voltage converter using LM358

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ark5230

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I am trying to make a current to voltage amplifier.
The current range is 0 - 200 µA in to 1 KΩ.
The expected output is 0 - 5 V.
The question is that is it possible to do this using single power supply op amp LM358
 

Hi,

It would depend on the supply voltage. Page 5 of the datasheet says Vout goes to V+ -1.5V.
 

What is missing, is your available power supply set.

Of course if the input compliance is or exceeds 5V
on the current source then your simplest I-V conversion
is just a dumb resistor. But the specified 1Kohm
impedance doesn't give you the gain you need.

If you want a (virtual) ground reference for the current
to push into then a transresistance amp (op amp w/
feedback resistor) is the way to go, but that will be
an inverting amplifier. To hold virtual ground you would
need an opposing-polarity supply (split supply would be
ideal). To put it back right-side-up you might add an
inverting stage (use a dual op amp).
 

You can do it like this

CV.PNG

Be aware of LM358/LM324 output voltage limits. The lower limit can be slightly pulled down by adding load resistance. The characteristic isn't exactly modelled in the commonly used SPICE models, need to review the datasheet.
 

Hi,

Why do you need to use the 1k?

If you use a 25k resistor you get a perfect 200uA to 5V I-V converter.
No need for Opamps with their drawbacks(offset, noise, power supply, part count...)


Klaus
 
Hi,
To make a non-inverting converter, which is, as far as I understand, the OP's objective.
Click to expand...
Misunderstanding.
I referred to the OP´s "1k" of post#1.

Klaus
 
The specification suggests that the current source compliance is limited, but of course we don't know.
 
To measure positive polarity, using a single-ended supply, means that in a sense you are using one-half of the op amp's circuitry, or rather its output stage.

You can do something similar with a single transistor. Common base operation gives you a non-inverting I-to-V amplifier.

measure 200uA thru 1k via common base NPN 5VDC supply.png

With careful adjustment you can customize response so output is close to linear proportion.
 

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