Variable Capacitor Basics

As we know, capacitors are of two types: fixed capacitors and variable capacitors. A fixed capacitor provides a fixed capacitance in an electronic circuit, while a variable capacitor provides varying capacitance as needed in the circuit.

It’s commonly used to tune a radio receiver to the desired frequency.

A variable capacitor is composed of two sets of metal plates that are parallel to each other. One plate is fixed, and the other plate moves on a spindle within the fixed set. Both of these plates are separated by a dielectric, which can be either air or some solid material.

For some applications, two or more air-spaced type capacitors are ganged. This means that the capacitance in several circuits is changed together when the spindle is rotated.

The maximum capacitance achieved with fully overlapped plates is about 500 pF. Trimmers and preset capacitors are also used as variable capacitors for many applications.

There are also mica capacitors of the compression type, in which mica sheets are compressed more or less by tuning a screw. This results in a change in capacitance.

Variable Capacitor Manufacturers

Here are a few of the reputed variable capacitor manufacturers:

1. muRATA
2. Vishay
3. Voltronics Corporation
4. Johanson manufacturing corporation
5. Mouser electronics
6. ECI