Impedance: A beginner’s guide -or- how I learned to stop worrying and let Matlab do the work.

Impedance is a concept that some people say they understand, but deep in their heart of hearts they know they don’t. I’m going to try and help you get a more helpful conceptual understanding of it. But to try and entice you into learning about it, I’m going to pose you a question: where does a sine wave go, when it’s amplitude is zero?
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Detecting Light: Simple Photodiode Amplifier

Light is great stuff. It provides energy to the ecosystem stuff, preventing earth from being a blue and grey desolate rock, but more importantly, it is really helpful in the lab. I use it mainly in a beam break manner, so I can tell whether something is in a region of space, without touching it. But it can also be used to detect distance, movement, temperature and pretty much anything else you can think of, so long as you can detect the light accurately enough. And this is exactly what I’m about to teach you: how to detect light, amplify it, and make it work for you. The following circuit isn’t designed for ulta-high precision, but it can be made with less than 10 components, and only requires one design decision.

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