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I have found an opamp schematic that I don't understand. As far as I know a transimpedance amplifier "converts" my input current into an output voltage. But in this case the positive and the negative inputs are driven by an input current.

Does that mean that my current difference will be amplified?

enter image description here

I tried to simulate this schematic in LTspice, but unfortunately I cannot explain this schematic to myself.

It would be very helpful if someone can name this schematic.

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    \$\begingroup\$ what are your inputs here? you can't claim that pin 3 is connected to a current input, because by (idealized) definition, no current can flow into the inputs of an opamp. \$\endgroup\$ Commented Nov 19, 2018 at 12:02
  • \$\begingroup\$ The inputs are connected to a voltage source. \$\endgroup\$
    – user118405
    Commented Nov 19, 2018 at 12:03
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    \$\begingroup\$ The inputs are connected to a voltage source Then why not show that in the schematic. The circuit around the opamp is an essential part of how it will behave. In your circuit the + input should be connected to a voltage source of a value "in between" the supply voltage. To the - in out you then apply an input current. \$\endgroup\$ Commented Nov 19, 2018 at 12:08
  • \$\begingroup\$ Does that mean that my current difference will be amplified? No, an opamp is a voltage amplifier. So the voltage difference between + and - inputs is amplified. To learn how to use opamps, read: Opamps for everyone: cypress.com/file/65366/download \$\endgroup\$ Commented Nov 19, 2018 at 12:11

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A simple trans-impedance amplifier is this:

enter image description here

Here is the link to it.

This is a simple one, there can be different variations. You are correct when you say that an output voltage will be produced from the current source input you give. But obviously no current goes into the Op-Amp terminals.

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  • \$\begingroup\$ Thank you, I'd like to know what happens when there are two different current sources on + and - port of my opamp? \$\endgroup\$
    – user118405
    Commented Nov 19, 2018 at 12:26
  • \$\begingroup\$ when there are two different current sources on + and - port of my opamp? That will not work with this type of circuit. It can only handle one input current. \$\endgroup\$ Commented Nov 19, 2018 at 12:29
  • \$\begingroup\$ @thirstyAndreas If you apply a current source directly to any one of the terminals of the Op-Amp it wouldn't work, the input impedance is very high. \$\endgroup\$
    – Rattle
    Commented Nov 19, 2018 at 12:29
  • \$\begingroup\$ @thirstyAndreas Happy to help! \$\endgroup\$
    – Rattle
    Commented Nov 19, 2018 at 12:33

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