how do i connect a photodiode detecting laser?
The usual configuration is to use a transimpedance amplifier. This takes the current output of the photodiode and converts it to a low-impedance voltage signal.







simulate this circuit &ndash; Schematic created using CircuitLab

The gain of the amplifier is set by R1. The maximum gain achievable without ringing in the response will depend on the op-amp used. C1 is used to reduce high-frequency noise. OA1 is chosen based on noise and bandwidth. The parasitic capacitance at the inverting input of the op-amp has a strong effect on overall performance.

With an appropriately chosen op-amp this circuit can be used up to at least 40 or 50 MHz (probably someone will comment that it is usable at higher frequencies --- 40-50 MHz is just the highest where I've seen it used). For higher frequencies you may need a specially designed receiver, which is basically the same circuit but integrated to reduce parasitics.