Re: Electronics theory questions: diodes, opamps etc...
Ok, here's the simple explanation (I hope I get it right.
)
A Diode has two connections, it only allows current to flow in one direction. You can use it as a rectifier (to convert alternating current to direct current), you can use it to block current flow (up to it's breakdown voltage), and you can clip a signal by taking advantage of it's properties. When current flows through a Diode, the voltage is "dropped" by whatever the spec of the diode is. In a guitar distortion circuit, it basically allows the input waveform to exist until it hits the voltage drop of the diode, then the diode effectively "clips" the waveform at that voltage. (The higher the voltage drop, the less the clipping). Also, different diodes will behave differently at that threshold.
There are several types of Transistors, I think a visit to Wikipedia can give you some more information. A Bipolar Junction Transistor is basically two Diodes back to back. You can use them as a current controlled current amplifier. A FET is another type of transistor that is basically a voltage controlled current amplifier. You can use them as the basic diodes they are made of, but the idea is to take advantage of the semiconductor properties to amplifiy current.
An Op Amp is made up of transistors internally, and is effectively a voltage controlled voltage amplifier. It's not a "powerful" transistor, in fact you can't expect much current flow out of an Op Amp without destroying it. It is, however, powerful to the designer because it makes it easy to design a voltage amplifier. (Generally a basic amplifer circuit will use an Op Amp to boost the voltage, then a power transistor to supply the current necessary to drive the load)
If I recall correctly, a TS type pedal amplifies the voltage with an Op Amp so the signal voltage is above the voltage drop level of the diodes, so they clip the signal. As you guessed, an Op Amp or a Transistor can impart it's own clipping, usually when you exceed the suplly voltage (device can't amplify the entire signal accurately) and also if you exceed some of it's design specifications (voltage slew rate, etc.)
I think that's pretty accurate, it's all from memory so I hope someone that actively uses this stuff can look it over.
