The trimmer capacitor is actually a variable capacitor, but the range of capacitance change is small, usually only a few picofarads to tens of picofarads.
Trimming capacitors are divided into mica trimming capacitors, ceramic-mediated trimming capacitors, film trimming capacitors, pull-line trimming capacitors, and so on. It is often used as a compensation capacitor or correction capacitor in various tuning and oscillation circuits. Capacitors that can be adjusted within a small range and can be fixed to a certain capacitance value after adjustment are called trimmer capacitors, and semi-trimmer capacitors can also be seen. When adjusting, change the distance or area between the two pieces. The trimmer capacitor is made of two or two sets of small metal shrapnel sandwiched between the dielectric. As shown in the figure, the shape of the semi-adjustable capacitor. Semi-adjustable capacitors generally do not have a handle and can only be adjusted with a screwdriver, so they are often used in places that do not need to be adjusted frequently. Semi-tunable capacitors are used as compensation capacitors or correction capacitors in various tuning and oscillation circuits.

The main function is to adjust the resonant frequency with oscillating components such as inductance coils. The adjustable capacitor has the same function as the fixed capacitor in practical applications, but its flexibility lies in the ability to adjust the capacity. By changing this data, Realize the resonance of the circuit with inductance and other components. Usually an important indicator of adjustable capacitance is the level of resonance frequency. The higher the resonance frequency, the better its precision.