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Applications of Diodes

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Collection of diodes
Tim Ridley/Dorling Kindersley/Getty Images

The simplest semiconductor component, the diode, has an astonishing number of applications that are enabled by a number of practical and unique types of diodes that are vital in modern electronics.

Applications of Diodes

While only two pin semiconductor devices, there are a number of applications of diodes that are vital in modern electronics. Diodes are known for only allowing current to move in one direction through the component. This lets a diode acts as a one way valve, keeping signals where they need to be or routing them around components. While diodes only let current move in one direction, each type of diode acts differently, making a number of useful applications for diodes.

Some of the typical applications of diodes include:
  • Rectifying a voltage, such as turning AC in to DC voltages
  • Isolating signals from a supply
  • Voltage Reference
  • Controlling the size of a signal
  • Mixing signals
  • Detection signals
  • Lighting
  • Lasers diodes

Power Conversion

One significant application of diodes is to convert AC power to DC power. A single diode or four diodes can be used to transform 110V household power to DC by forming a half-way (single diodes) or a full-wave (four diodes) rectifier. A diode does this by allowing only half of the AC wave form to travel through it. When this voltage pulse is used to charge a capacitor, the output voltage appears to be a steady DC voltage with a small voltage ripple. Using a full wave rectifier makes this process even more efficient by routing the AC pulses so both the positive and negative haves of the input sine wave are seen as only positive pulses, effectively doubling the frequency of the input pulses to the capacitor which help keep it charged and deliver a more stable voltage.

Diodes and capacitors can also be used to create a number of types of voltage multipliers to take a small AC voltage and multiply it to create very high voltage outputs. Both AC and DC outputs are possible using the right configuration of capacitors and diodes.

Demodulation of Signals

The most common use for diodes is to remove the negative component of an AC signal so it can be worked with easier with electronics. Since the negative portion of an AC waveform is usually identical to the positive half, very little information is effectively lost in this process. Signal demodulation is commonly used in radios as part of the filtering system to help extract the radio signal from the carrier wave.

Over-Voltage Protections

Diodes also function well as protection devices for sensitive electronic components. When used as voltage protection devices, the diodes are non-conducting under normal operating conditions but immediately short any high voltage spike to ground where it cannot harm an integrated circuit. Specialized diodes called transient voltage suppressors are designed specifically for over-voltage protection and can handle very large power spikes for short time periods, typical characteristics of a voltage spike or electric shock, which would normally damage components and shorten the life of an electronic product.

Current Steering

The basic application of diodes is to steer current and make sure it only flows in the proper direction. One area where the current steering capability of diodes is used to good effect is in switching from power from a power supply to running from a battery. When a device is plugged in and charging, for example a cell phone or uninterruptible power supply, the device should be drawing power only from the external power supply and not the battery and while the device is plugged in the battery should be drawing power and recharging. As soon as the power source is removed, the battery should power the device so no interruption in noticed by the user.

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