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current to voltage converter

Holden C

Feb 6, 2014
1
Joined
Feb 6, 2014
Messages
1
i read when we use a transconductance amplifier or current to voltage converter , the output voltage will be the multiplication of negative of input current by feedback resistor. V (out)=-i (in)* R
so for example if we have a 1 nA input current we will have a -0.1 V at the output while the feedback resistor is 100 M ohm. So my question is that why we bother to use an op-amp? i mean why we don't run the current directly through the R?
i read somewhere it is related to power gain but i don't really understand this. can anyone help me out to understand this? please explain somehow that a chemist could understand!
Thanks
 

kpatz

Feb 24, 2014
334
Joined
Feb 24, 2014
Messages
334
The current through a resistance is a function of the voltage and resistance (I=V/R). Therefore, a resistor won't convert current to voltage; more the opposite.

Also, transconductance amplifiers convert voltage to current, not the other way around. Maybe you're referring to a transimpedance amplifier?
 
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