Varactor diodes are typically fabricated using semiconductor materials like silicon or gallium arsenide. The construction is similar to regular diodes, but with a specific design to optimize the capacitance variation.
The primary function of a Varactor diode is to change its capacitance with the applied voltage. In its reverse-biased state, the diode exhibits a variable depletion region that changes with the voltage across it. As the voltage increases, the depletion region width decreases, leading to an increase in capacitance. Conversely, decreasing the voltage results in a wider depletion region and lower capacitance.
The most significant characteristic of Varactor diodes is their ability to vary capacitance with applied voltage. This property makes them useful in applications such as voltage-controlled oscillators (VCOs) and frequency tuning circuits.