What is Trimmer Capacitor : Working & Its Applications

The variable capacitor is one type of capacitor whose capacitance value can be changed when you change it either mechanically or electrically. These capacitors include a set of metallic plates where one plate is fixed & the other plate is changeable. These capacitors provide capacitance values that range from 10pF to 500pF. There are two types of variable capacitors available Tuning capacitor & Trimmer capacitor. These capacitors are used for tuning LC circuits of radio receivers and for impedance matching within antennas, etc. So this article gives brief information about one of the types of variable capacitors namely – the Trimmer capacitor, its working, and its applications.

What is Trimmer Capacitor?

A type of variable capacitor that is used for calibration & recalibration in equipment throughout manufacturing otherwise servicing is known as a trimmer capacitor. This capacitor is placed on a printed circuit board directly, This capacitor is also known as a variable capacitor which is not expensive as compared to full-sized variable capacitors.

These are mainly used in a circuit to primarily set the frequency values of oscillator, rise & fall times, latencies, etc. The Trimmer capacitor symbol is shown below. These capacitors are available in nail sizes that can be tuned in a certain range for their capacitance according to the circuit specifications. Trimmer capacitors are related to presets based on the functions they perform. The capacitance of these capacitors is small normally below 100pF.

Pin Configuration

The trimmer capacitor pinout is shown below which includes three pins that are discussed below.

This capacitor includes three pins where one is connected to an inactive plate, one to a rotating plate & the other pin is the common pin. The capacitance of this capacitor can be changed through a screwdriver.

In this capacitor, the movable plate is available in a semi-circular shape. Here, the capacitance of this capacitor mainly depends on the opposite region of the fixed plate & movable semi-circular disk. Once the opposite region is larger, then the value of capacitance can also be higher.

Construction

The trimmer capacitor construction is similar to the variable capacitor. So this capacitor construction can be done with semi-circular metal plates where one plate is fixed and another plate can be turned through a screwdriver.

The capacitance can be changed by turning the shaft through the operator to increase or decrease the amount of overlap between the two plates. The precision can be enhanced by allowing several turns in between the lowest & highest settings through gear mechanisms.

This capacitor can also be constructed by placing a metallic screw within a non-conductive threaded cylinder. Here, this screw signifies one electrode so by turning this screw, the distance among the two plates of the capacitor can be changed, and also capacitance can be changed. This type of design is applicable in microwave & RF applications.

Working

The working principle of the Trimmer capacitor is very simple like its structure. The metal screw on the capacitor can be rotated to change the capacitance. Once the capacitor’s metal plate overlaps the remaining two semi-circular form metal plates, then the capacitance will be at the highest magnitude.

Once the plate is turned in various positions then capacitance can be reduced and it is minimum once the metal plate is arranged reverse to other metal plates. The change takes place when the storage capacity of the electric field between the metal plates varies & it will be reduced once the metal plate is arranged quite opposite to the other.

Types of Trimmer Capacitor

Trimmer capacitors are available in two types air trimmer and ceramic trimmer which are discussed below.

Ceramic Trimmer Capacitor

Ceramic trimmer capacitors are very small and thin capacitors that include external dimensions L x W x H as 1.5 x1.7 x 0.85 mm. The construction of this capacitor is unique without using plastic material to provide better soldering heat resistance to keep outstanding characteristic performance.

These capacitors are applicable for high-frequency circuits because of 6.2 GHz high self-resonant frequencies. The applications of these capacitors include crystal oscillators, Bluetooth, crystal filters, mini tuner packs like FM, TV, etc.

Air Trimmer Capacitor

Air trimmer capacitors have a concentric tubular design, used especially for RF applications. These capacitors have multiturn, so provide an excellent resolution and temperature stability. The self-locking constant torque mechanism of this capacitor provides uniform torque, less ESR & less dynamic tuning noise. These capacitors are applicable in signal processing, RF communications, oscillator, interstate coupling, filter tuning, crystal trimming, impedance matching & the MRI & NMR industries.

Trimmer and Variable Capacitor Differences

The difference between a trimmer capacitor and a variable capacitor includes the following.

Advantages and Disadvantages

The advantages of a trimmer capacitor include the following.

• These are small in size.
• Not expensive.
• Available on tape and reel packaging.
• They provide up to 40pF of a significant amount of capacitance.

The disadvantages of a trimmer capacitor include the following.

• Mediocre temperature stability.
• They cannot be turned through a great amount of precision.

Trimmer Capacitor Applications

The trimmer capacitor uses include the following.

• These capacitors are used to fix oscillator frequency values, rise & fall times, and other variables within a circuit.
• These capacitors are used where a capacitance value is needed to be matched to a particular circuit in the manufacturing process.
• This is mostly used in the production phase.
• These are applicable in high-frequency applications like frequency tuning of microwave & RF filters.
• These components are used in equipment calibration once it is manufactured.
• These capacitors are normally used for matching and tuning applications within RF circuits.
• These are applicable where high precision is required.

Thus, this is all about an overview of a trimmer capacitor and its working with applications. The selection of any capacitor can be done based on some essential factors like value of capacitance, frequency, rated peak current, temperature, tolerance, type of capacitor, dissipation factor, etc. Here is a question for you, what is a tuning capacitor?