Diodes

Simple forward-biased diode circuit. To forward-bias the diode, the voltage across it from anode (+) to cathode (-) must exceed its forward-bias threshold voltage. When forward-biased, the excess electrons from the cathode (-) easily flow to the excess holes in the anode (+), so "conventional" current effectively flows freely from anode (+) to cathode (-): the diode is "on". When reverse-biased, the excess electrons arriving at the anode (+) cannot easily pass through to the cathode (-), due to the excess electrons already there, so "conventional" current effectively does not flow from cathode (-) to anode (+): the diode is "off". Constraints: When forward-biased, the diode drops its forward-bias threshold voltage across it, but does not otherwise limit current through it. Therefore another component such as a resistor must be used to limit the current. The resistor must be chosen such that: - the total current through the circuit does not exceed the maximum current of the power supply; - the current through the diode does not exceed its maximum forward current rating; - the power dissipated by the resistor does not exceed the resistor's maximum power rating. TODO: diode as a switch for AC; peak detector/envelope detector/AM demodulator; voltage doubler/voltage multiplier