What Are the Characteristics of an Ideal Silicon Diode?
A diode is an electrical switch commonly made of semiconductor material, such as silicon. It consists of two terminals: positive (anode) and negative (cathode). It is often used as a rectifier, which is a device that converts AC to DC with current flowing in one direction. Rectifiers can be found in electronic components such as radios, DC power supplies and high-voltage transmitters. Diodes take on many forms, such as vacuum tube diodes, semiconductor diodes and mercury-arc valves. A diode operates in conjunction with a resistor within a circuit.
Voltage Direction The direction electrons flow in a diode is characterized by forward and reverse modes. In a forward-biased diode, current flows in a positive direction, whereas in a reverse-biased diode, current flows in a negative direction. Here's another way to understand it:
- forward-biased diode = on (or "turned on")
- reverse-based diode = off (or "cut off")
Ideal Diodes A reverse-biased diode is said to be an open circuit. But when the diode is on, it acts as a short circuit. Ideally, the diode operates as an open nonlinear circuit with a fixed, constant voltage drop. This model is favored in the engineering field due to its simplicity. It is based on the concept that "forward conducting" has a minor fluctuating voltage drop from about 0.6-0.8 volts, with the assumption that the amount of voltage is constant at 0.7V.
The circuit can only be analyzed as linear if the voltage signal doesn't exceed one or more break points. Additionally, the ideal diode has zero resistance to current flow in one direction and high resistance in the opposite direction.
Conclusion Diodes allow current to flow freely in one direction while limiting flow in the opposite direction. The purpose of a forward-biased diode is to allow current to flow in a forward direction, while restricting current to flow in the reverse direction. A reverse-biased diode reflects negative voltage. The most common diodes are semiconductor-based.
