Vaihtokapasitanssi

Vaihtokapasitanssi, also known as variable capacitance or sometimes tunable capacitance, refers to a component whose capacitance value can be intentionally changed. This is in contrast to a fixed capacitor, where the capacitance is determined by its physical construction and remains constant. Variable capacitors are essential in electronic circuits where adjustments to the resonant frequency or impedance are required.

The most common type of variable capacitor is the trimmer capacitor, often used for fine-tuning in radio circuits or for calibrating instruments. Another well-known type is the tuning capacitor, typically found in older radio receivers, where it is mechanically linked to a dial to select different stations. These types often work by altering the overlap area of two sets of conductive plates or by changing the distance between them.

In some applications, capacitance can be varied electronically. Varicap diodes, for example, exhibit a capacitance that changes with the applied reverse voltage. This property is exploited in voltage-controlled oscillators (VCOs) and frequency modulators. The ability to alter capacitance dynamically makes these components crucial for tuning, frequency selection, and signal processing in a wide range of electronic devices.