Re: photodetector amplifier
Your intention is rather unclear. By placing a laser in front of a photo transistor, it will fully saturate (as your measurement
clearly shows), there's nothing to amplify in this case.
Without knowing the power supply, nothing can be said about failure of your amplifier. Also you should show the intended
photo detector connection. What makes you think to need a multi stage amplifier with your photo detector? What's the intended light
source and expectable intensity?
Photo transistors have data sheets, you should be able to calculate the photo current for a specific measurement setup and
determine, if an amplifier is needed, or if the intensity is possibly too high without any amplifier, as in your test.