Presto Electro

Electronics I is a very mysterious title for a class. When I enrolled in it last semester I didn't have any idea what to expect. I could have looked up the course summary in the online course catalog, but I like surprises. I also completely forgot about the course summaries in the catalog until just now. Yeah.

Anyway, I'm taking Electronics I this semester, and the second unit is all about Diodes. The first unit was Op-Amps-- fascinating, but probably too complex to summarize in a single blog. Diodes, on the other hand can be represented by this very simplified model:

The "Ideal Diode" works like a little switch. It turns "Off" when the current tries to flow one way, and turns "On" when it goes the other direction. It's like a turnstile or a one-way street, except instead of people or cars, it organizes electrons. This behavior allows for all sorts of clever manipulation of current. Rectification was the focus of last week's class, but diodes can also be used for things like diode logic and audio manipulation.

Whenever an electronic component can be used to manipulate AC signals, I start imagining what sort of impact these things could have on audio signals. And I'm definitely not the only one. Non-linear components are golden when it comes to distortion!

Here is a great example of diode use in action. This circuit takes advantage of the fact that real (non-ideal) diodes need a little kick-start before they flip "on". If you apply more than zero, but less than (usually) .7 volts to an LED, it stays off. If you go over that threshold, if flips "on". In this case, it flips on and connects the guitar signal to ground, and chops off the top of the peak of the signal.

I've found approximately a million articles about clipping and distortion, but NONE of them have sound!!! I think I'm going to have to bring a guitar into the lab tomorrow…