Although the functions of current limiting diodes and current limiting resistors in circuits are to limit current, their working principles and characteristics are different.
1. Current limiting resistor:
The current limiting resistor is connected in series in the circuit to increase the total resistance and reduce the magnitude of the current. Its main function is to protect circuit components from damage caused by excessive current. Current limiting resistors can also share a portion of the voltage, allowing other circuit components to operate normally within a safe voltage range. In addition, current limiting resistors help maintain stable output voltage during load changes. The calculation formula for current limiting resistance can be (R=V supply - V component)/I, where V supply is the power supply voltage, Vcomponent is the voltage of the component, and I is the required current.
2. Current limiting diode (constant current diode):
A current limiting diode (also known as a constant current diode or CCD) is a special type of diode that allows for a constant amount of current at its maximum limit. Its working principle is similar to the voltage limitation of a Zener diode, where even if the voltage at both ends changes, the current will not change. The current limiting diode only operates under forward bias and does not function under reverse bias. It is a protective device used to protect circuits from the effects of overcurrent or short circuit. A current limiting diode is composed of an N-channel JFET, which allows the current to rise to a specific limit and remain constant, known as the pinch off current.
In summary, current limiting resistors limit current by increasing resistance and are suitable for various circuits, while current limiting diodes use their special voltage current characteristics to maintain a constant current under forward bias and are suitable for situations that require a constant current source. Both are important current control components in circuit design, and the choice of which to use depends on specific application requirements and circuit design.
