As a semiconductor expert with extensive experience in the field of electronics, I am well-versed in the nuances of various electrical properties of semiconductor devices. Let's delve into the differences between knee voltage and breakdown voltage, two critical parameters that are essential for understanding the behavior of semiconductor diodes.

Knee Voltage refers to the voltage level at which a diode begins to conduct significantly. It is also known as the "cut-in voltage." This term is used to describe the point at which the diode transitions from a high-resistance state to a low-resistance state. The knee voltage is typically associated with silicon diodes, which have a knee voltage around 0.7 volts, and germanium diodes, which have a lower knee voltage, typically around 0.3 volts. This voltage is the minimum required to forward-bias the diode and enable it to conduct current. It is an important parameter for diode operation in circuits, as it defines the threshold at which the diode starts to act as a conductor.

Breakdown Voltage, on the other hand, is the maximum voltage that a diode can withstand before it breaks down and allows a large current to flow, potentially leading to device failure. This is the reverse voltage at which the PN junction of the diode breaks down. The breakdown voltage is a safety limit that ensures the diode operates within safe parameters to prevent damage. It is a critical specification for applications where the diode may be exposed to high voltages, such as in power electronics or voltage regulation circuits.

The key differences between knee voltage and breakdown voltage are as follows:


1. Direction of Voltage: Knee voltage is associated with the forward biasing of the diode, where the diode starts to conduct current in the forward direction. Breakdown voltage, however, is related to the reverse biasing, where the diode is subjected to a high voltage in the opposite direction.


2. Purpose: Knee voltage is the threshold for diode conduction, indicating the start of significant current flow. Breakdown voltage is a safety limit, indicating the maximum voltage the diode can handle before potential damage occurs.


3. Operational State: At knee voltage, the diode is entering its active region, ready to conduct current efficiently. At breakdown voltage, the diode is nearing a state of potential failure, where it may allow excessive current flow that could damage the device.


4. Material Dependence: The knee voltage can vary depending on the material used in the diode, with silicon and germanium having different typical knee voltages. Breakdown voltage is also material-dependent but is more about the structural integrity and design of the diode rather than the material's intrinsic properties.


5. Circuit Design Implications: In circuit design, knowing the knee voltage helps in determining the minimum forward voltage required to activate the diode. Understanding the breakdown voltage is crucial for ensuring that the diode is not subjected to voltages that could cause it to fail.

In summary, while both knee voltage and breakdown voltage are important parameters for diode operation, they serve different purposes and are indicative of different operational states of the diode. Designers must consider both when working with diodes to ensure optimal performance and reliability.

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Breakdown voltage: The reverse voltage at which the PN junction breakdown occurs is called as breakdown voltage. ... Knee voltage is also known as --cut-in-voltage". The minimum amount of voltage required for conducting the diode is known as --knee voltage-- or --cut-in-voltage".read more >>