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Constant-Current Diode

Constant current diodes are electrical devices that regulate electrical currents and flow to a high range. Unlike common diodes, constant current diodes are not commonly used anymore, instead, have been replaced by Junction Gate Field-Effect Transistors (JFET or JUGFET). Constant current diodes served many purposes before being replaced, such as medical purposes and fiber optical communications. 

Diodes Background

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Like most diodes, constant current diodes are also semiconductor devices that have two ends: an anode and a cathode. An anode is a positively charged conductor that allows electricity to enter. On the other hand, a cathode is a negatively charged electronic conductor that allows electricity to leave. While electricity is flowing forward, the electrons present will flow the opposite way so instead of going from the anode terminal to the cathode terminal it goes from the cathode terminal to the anode terminal.[1]

Because it is a semiconductor, this means that it is an electrical component commonly used to transmit energy.

There are many kind of diodes that exist for example, the constant current diode. The most common diodes that are being used in current devices are Silicon and Germanium diodes.[2] When applying diodes, they are mostly used to power devices such as lights. Currents only flow in one direction unless it is a special type of diode, such as a Zener diode. Some diodes also serve the purpose of converting energy such as a silicon diode or a gallium nitride diode.

When the current of a diode is going in a direction, it is called forward bias. If it tries to move in the opposite direction it originally moved that is called a reverse biased. In constant current diodes, there is only a forward bias flow.

Constant Current Diode function

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Similar to a Zener diode, the constant current diode also regulates voltage at a particular current source.[3] The current source sends or absorbs an electric current which is independent from a voltage that is across from it. However, it also keeps the current consistent instead of the voltage. The voltage being sent through the voltage may be changed.

Constant current diodes allow the current to get regulated at a wide voltage range. If more current were to be attempted to be sent through the diode, the diode would push the current and resist the current. When resisting the current, the voltage will fall.[4]

Transistors are semiconductor devices with three connections. They are capable of acting like a gate for electrical signals.[5] Constant current diodes consists of JFET-transistors, which also behave like a two terminal transistor[6] but with three terminals instead of two like the diode. Often, the diodes are said to behave like the transistors. JFET transistors allow currents to be controlled with the application of lower power electrical signal.[7] Because it can be controlled, the voltage can be changed but the current running through the diode can not be changed.

The kind of JFET transistor being used to create a constant current diode is an n-channel JFET. This transistor is being used because it is mostly composed of electrons.

Common constant current diodes are often sorted out by their certain characteristics. The characteristics in which they are separated by are limiting voltage, power consumption, packing type and nominal regulator current.[8] Their common voltages are the following: 1.7 V, 2.8 V, 3.1 V, 3.5 V and 3.7 V.

There are several type of constant current diodes. For instance, we can begin by introducing the  1N528-1N5314 series of diodes.[9] This series of diodes are used in parallel circuits. In this circuit, higher currents can be obtained.

Uses

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The practical uses of Constant Current Diodes are many. For example, the diodes can be used for waveform generator circuits, battery charger, and the creation of circuits such as the timing circuit.[10]

Not only this, but constant current diodes can also be used as a shunt current regulator.[11] A shunt current regulator provides a path for current to flow.

Constant current diodes have also been used for medical purpose. People who were hospitalized and the hospital employees often faced the struggle of their equipment not working. In addition to the damaged equipment, some times their equipment would shock them and the shocks would vary from a small shock to threatning levels. With the constant current diodes, the levels of currents being sent through were being regulating due to their small resistance. [12]

Another use for constant current diodes was for fiber optical communications. In fiber optical communications, there is information that is being transmitted from one location to another with light pulses. The role the diode plays in this is that is regulates the current source being sent.[13]

References

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  1. ^ "Learn About Electronics - Diodes". www.learnabout-electronics.org. Retrieved 2015-11-05.
  2. ^ "Learn About Electronics - Diodes". www.learnabout-electronics.org. Retrieved 2015-11-04.
  3. ^ "What is a CLD" (PDF). Central Semi.
  4. ^ "Special-purpose Diodes : Diodes and Rectifiers - Electronics Textbook". www.allaboutcircuits.com. Retrieved 2015-10-21.
  5. ^ "transistor | a small device that is used to control the flow of electricity in radios, computers, etc". www.merriam-webster.com. Retrieved 2015-10-21.
  6. ^ "Constant Current Diode | ElectronicsTerms.com | Explanations | Examples". ElectronicsTerms.com | Explanations | Examples. Retrieved 2015-10-21.
  7. ^ "Introduction to Junction Field-effect Transistors (JFET) : Junction Field-effect Transistors - Electronics Textbook". www.allaboutcircuits.com. Retrieved 2015-10-21.
  8. ^ "Constant Current Diode | ElectronicsTerms.com | Explanations | Examples". ElectronicsTerms.com | Explanations | Examples. Retrieved 2015-10-21.
  9. ^ "Constant Current Diode | ElectronicsTerms.com | Explanations | Examples". ElectronicsTerms.com. Retrieved 2015-11-03.
  10. ^ "Current Limiting Diodes Information | IHS Engineering360". www.globalspec.com. Retrieved 2015-10-21.
  11. ^ "Special Applications Diodes". wps.prenhall.com. Retrieved 2015-11-04.
  12. ^ Fish, Raymond M. (1970-10-01). "The Use of Constant Current Diodes in Preventing Electrical Shock from Hospital Equipment". IEEE Transactions on Biomedical Engineering. BME-17 (4): 351–351. doi:10.1109/TBME.1970.4502766. ISSN 0018-9294.
  13. ^ DaiQiang, Wang; Qiao, Liu; Zhao, Ding; LiangRong, Li; Yi, Wang (2008-08-01). "Application of constant-current diodes in optical fiber communication". 2nd International Conference on Anti-counterfeiting, Security and Identification, 2008. ASID 2008: 336–339. doi:10.1109/IWASID.2008.4688416.
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