variable capacitor
Capacitors with variable capacitance are the mechanical variable capacitor and the trimmer, and the capacitance diode is an electronic component with variable capacitance. These are used for tunable frequency adjustments in oscillating circuits, oscillators or filters.
The classic variable capacitor (variable capacitor), known from the early days of radio technology, is still used in special oscillators for frequency tuning. A variable capacitor consists of two metal plate packs, one fixed and one movable, which interlock in the form of a comb. The fixed plate pack is the stator, the movable one the rotor. The dielectric between the electrodes can be air or an insulating film. The capacitance of the variable capacitor increases the further the rotor is rotated into the stator. The overlap areas of the two electrodes thus determine the capacitance, which can be changed by the angle of rotation.
The shape of the metal electrodes is adapted to the tuning behavior. A linear, logarithmic or user-specific tuning behavior is achieved by shaping. The spacing of the electrodes, i.e. the metal plates, is decisive for the dielectric strength of the variable capacitor.
Trimming capac itors, or trimmers for short, are scaled-down variable capacitors that operate with two metal-coated plates and are adjusted with a screwdriver. They are only used for fine tuning of oscillator or filter frequencies.