Types of Diodes

Today there are many varieties of diodes, which can be grouped into one of several basic categories.

Power Rectifier Diodes

The rectifier diode is usually used in applications that require high current, such as power supplies. The range in which the diode can handle current can vary anywhere from one ampere to hundreds of amperes. One common example of diodes is the series of diodes, part numbers 1N4001 to 1N4007. The “1N" indicates that there is only one PN junction, or that the device is a diode. The average current carrying range for these rectifier diodes is about one ampere and have a peak inverse voltage between 50 volts to1,000 volts. Larger rectifier diodes can carry currents up to 300 amperes when forward biased and have a peak inverse voltage of 600 volts. A recognizable feature of the larger rectifier diodes is that they are encased in metal in order to provide a heat sink. Figure 10-204 illustrates a line drawing of some general purpose diodes.

Zener Diodes

Zener diodes (sometimes called “breakdown diodes") are designed so that they will break down (allow current to pass) when the circuit potential is equal to or in excess of the desired reverse bias voltage. The range of reverse bias breakdown-voltages commonly found can range from 2 volts to 200 volts depending on design. Once a specific reverse bias voltage has been reached, the diode will conduct and behave like a constant voltage source. Within the normal operating range, the zener will function as a voltage regulator, waveform clipper, and other related functions. Below the desired voltage, the zener blocks the circuit like any other diode biased in the reverse direction. Because the zener diode allows free flow in one direction when it is used in an AC circuit, two diodes connected in opposite directions must be used. This takes care of both alternations of current. Power ratings of these devices range from about 250 milliwatts to 50 watts.

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