Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Here's a good link I just found. Photo Detector Circuits
I think you can put the photo transistor as a voltage divider at the base of a transistor and it can work as a switch (Instead of using the op-amp).