What devices with varactor diode?

Varactor diodes, also known as varicap diodes, are commonly used in devices such as voltage-controlled oscillators (VCOs), frequency modulators, and tuners in radio and television receivers. They exploit the voltage-dependent capacitance of the diode to allow for adjustable tuning in circuits. Other applications include phase-locked loops (PLLs) and RF filters, where they help in frequency stabilization and modulation. Additionally, varactor diodes are used in communication systems for channel selection and signal processing.