Since I never understood op-amps from reading or practicing problems I wanted to build a circuit to probe around and use different resistor values to set the amplification....
I recommend EEVBlog’s OpAmp tutorial. His explanation is pretty simple to understand. Basically there are two rules (note these rules are ideal, but the exceptions can usually be ignored):
No current flows into the inverting and non-inverting inputs.
For negative and positive feedback circuits, the OpAmp wants to keep the inputs the same by changing its output, and will sink power to its positive or negative power rails to achieve this.
What I've done is take a large 2n3055 BJT NPN power transistor, and decap it (it is a large metal-can type). Then I carefully removed any coating from the exposed silicon (it typically has a dab of silicone potting compound on it)....
I work with a lot of particle detectors. Instead of this, I recommend a photo diode and laser diode. Light dispersal particle counting is relatively easy to pull off by comparison to scraping off coating and all that. You could even use a very small segment of solar panel and a light source or an IR detector and IR LED similar to a smoke detector.
Non-Inverting LM358 Circuit Not Working (discuss.tchncs.de)
Since I never understood op-amps from reading or practicing problems I wanted to build a circuit to probe around and use different resistor values to set the amplification....
Transistor particle detector not functioning as expected (voltage.vn)
What I've done is take a large 2n3055 BJT NPN power transistor, and decap it (it is a large metal-can type). Then I carefully removed any coating from the exposed silicon (it typically has a dab of silicone potting compound on it)....