I need some basic advice for impedance matching: I have a photodetector (Det01CFC from Thorlabs, https://www.thorlabs.com/drawings/275cb418cdc2cf1f-A2E46103-D9C0-3581-4553E3D3CA93AD83/DET01CFC-Manual.pdf) that generates a current. For my experiment, I would like to amplify this signal with an amplifier to subsequently read it out with a digital oscilloscope.
The amplifier that I use is the LNA-1440 (https://rfbayinc.com/products_pdf/product_88.pdf) with an input impedance of 50 Ohm. Since the input impedance of the amplifier matches the source impedance of the photodetector, I connected them directly with an SMA-cable.
The problem that I am facing right now is that the signal gets attenuated for frequencies larger than a few MHz, i.e. it seems as if my circuit acts as a low pass filter. Do you have an idea why this could be the case?
Thank you very much for your advice!