What is Constant-current diode?
Constant-current diode is an electronic device that limits current to a maximum specified value for the device. It is known as current-limiting diode (CLD), current-regulating diode (CRD).
These diodes consist of an n-channel JFET-transistor with the gate shorted to the source, which functions like a two-terminal current limiter or current source (analogous to a voltage-limiting Zener diode). They allow a current through them to rise to a certain value, and then level off at a specific value. Unlike Zener diodes, these diodes keep the current constant instead of the voltage constant. These devices keep the current flowing through them unchanged when the voltage changes. An example is the 1N5312. Note the negative VGS is required, as an example on the n-type junction-gate field-effect transistor 2N5457.
Types of Current Limiting Diodes
There are many different kinds of current limiting diodes. The most common types categorised by nominal regulator current, maximum limiting voltage, operating voltage, packaging type and power consumption.
The most common values for maximum limiting voltage are 1.7 V, 2.8 V, 3.1 V, 3.5 V and 3.7. V and 4.5 V. Nominal regulator current can have a range from 0.31 mA to 10 mA, with the most common nominal regulator current being 10 mA.
Applications for Current Limiting Diodes:
Current limiting diodes offer high performance and simplicity characteristics compared with bipolar transistors. They offer versatility in several circuit applications and superior performance regarding dynamic and impedance temperature drift. Some examples of devices using current limiting diodes are waveform generator circuits, timing circuits and battery chargers. Current limiting diodes can also be found as a constant current source for driving LEDs and can be used in order to replace holding coils in telephone connection devices.
Revision date 11 March 2017
Revision date 15 February 2018