The simplest semiconductor device—the diode—performs a variety of useful functions related to its core purpose of controlling the direction of the flow of electrical current. Diodes allow current to flow in only one direction.
Diodes Explained – The Basics of Diodes PN Junction Working Principle
Perfectly efficient diodes appear to be open circuits with a negative voltage, and otherwise appear to be short circuits. However, because diodes do suffer from some inefficiency, their current-voltage relationship is nonlinear. For this reason, you will want to consult a diode's datasheet to see a graph of the curve of any given diode's forward voltage versus its forward current, so that you can choose the right diode for your particular project.
Despite being simple two-pin semiconductor devices, diodes are vital in modern electronics. Some typical applications of diodes are:
An important application of diodes is in converting AC to DC. A single diode or four diodes convert 110V household power to DC by forming a half-wave (single diode) or full-wave (four diode) rectifier. The diode only allows half of the AC waveform to pass through it. When this voltage pulse charges a capacitor, the output voltage appears to be a steady DC voltage with little voltage ripple. Using a full-wave rectifier makes this process even more efficient by routing the AC pulses so that both the positive and negative halves of the input sine wave are seen as positive pulses only, effectively doubling the frequency of the input pulses to the capacitor, helping to keep it charged and providing a more steady voltage.
