# Current to voltage converter

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#### vishumittal

##### Newbie level 6
yes..that is why I asked you to help me!!!!!
But if you do not have any idea, it is fine.
Thank You so much.

#### godfreyl

strange project, my friend
... with requirements as clear as mud and no context.:roll:
I guess your scale is too big.... 10pA -10mA
A logarithmic scale may be more useful. The current could be passed through a diode, and the voltage drop across the diode sensed with a suitable opamp. CMOS opamps are available with bias currents less than 1pA.

#### vishumittal

##### Newbie level 6
According to me, I have provided you all the information, tell me what you don't understand.
I am using log graph.
Thanking You.

#### steinar96

##### Full Member level 1
You may try looking up logarithmic amplifiers. They are expensive though but they may handle the wide current range better

#### vishumittal

##### Newbie level 6
Can you help me in designing a circuit for shorter range?
Like 10pA-20nA.
Thank You.

#### FvM

##### Super Moderator
Staff member
Can you help me in designing a circuit for shorter range?
Like 10pA-20nA.
It's easy. Refer to the circuit from post #10, calculate a suitable feedback resistor value (500 Meg), change 741 against an "electrometer" OP with sub pA input current (e.g. OPA129) and you're done.

But does a linear, single range I/V converter solve the problem? It possibly does for the restricted 1:2000 range but surely can't for the original 1:10e9 range.
There are at least three possibly solutions:
- multiple ranges with manual selection
- autoranging
- non-linear characteristic like the said log curve

It looks you didn't yet think about a full project specification. I wonder if others (e.g. the project supervisor) did.

vishumittal

### vishumittal

points: 2
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