In a little hobby project I am trying to send data from one Arduino to another using a modulated laser and a photodiode.
On the sender side, the laser has a dedicated modulation input for up to 100kHz. The input is low-active and I connect it directly to the TX pin of the sender-Arduino serial port. Since the UART is low-active too, the laser is turned off, if the UART is idle, which is nice.
On the receiver side I have a photo diode and a transimpedance amplifier with an LM385 opamp. The output is wired to the RX of the receiver-Arduino.
Here is the problem: If the sender pulls TX to low (1), this causes the laser turn on (2). On the receiver side the photo diode is illuminated causing a current to flow (3) and the transimpedance amplifier to output a high signal at RX (4). In short: Sender TX low -> Receiver RX high.
I clearly need an inversion of the transimpedance amplifier's output: 5V -> 0V and 0V -> 5V. The inversion cannot be done in software in the receiver, since the UART of the Arduino cannot be configured to do that. Of couse I could add a 7404 with a NOT gate to the schematics. But would it be possible to change the transimpedance amplifier in a way that the output is inverted but it still stays a transimpedance amplifier with the performance advantages for my application?
Careful with the word "inverted" in the world of opamps. You have "inverting opamps" but that is something different. And I do not want to "invert" by making 5V -> -5V or something like that.