Trimmers, Variable Capacitors

Part Number	Description / PDF	Quantity
AT 27268 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V SMD	15
AT 27269 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V TH	15
118-110173 EXXELIA	CAP TRIMMER 0.6-4.5PF 500V TH	0
AT 27261 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V TH	9
118-110421 EXXELIA	CAP TRIMMER 0.8-8PF 500V SMD	0
AT 27263+CAP EXXELIA	CAP TRIMMER 0.3-1.2PF 500V SMD	15
AT 27274 EXXELIA	CAP TRIMMER 0.6-4.5PF 500V TH	15
118-31027 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V TH	0
118-110265 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V SMD	0
118-110233 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V TH	0
118-110252 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V SMD	0
AT 27283+CAP EXXELIA	CAP TRIMMER 0.4-2.5PF 500V SMD	15
AT 27271 EXXELIA	CAP TRIMMER 0.6-4.5PF 500V TH	9
AT 27291-SL EXXELIA	CAP TRIMMER 0.8-8PF 500V SMD	10
118-110170 EXXELIA	CAP TRIMMER 0.6-4.5PF 500V TH	0
AT 27260 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V TH	5
118-111574 EXXELIA	CAP TRIMMER 0.4-2.5PF 500V SMD	0
118-110232 EXXELIA	CAP TRIMMER 0.3-1.2PF 500V TH	0
AT 27285 EXXELIA	CAP TRIMMER 0.4-2.5PF 500V TH	10
118-31057 EXXELIA	CAP TRIMMER 0.4-2.5PF 500V TH	0

Trimmers, Variable Capacitors

1. Overview

Trimmer capacitors and variable capacitors are specialized capacitive components with adjustable capacitance values. Trimmers are semi-fixed capacitors designed for infrequent adjustments during device calibration, while variable capacitors allow continuous manual or mechanical tuning. These components are critical in analog circuits, RF systems, and precision electronics, enabling fine-tuning of frequency response, impedance matching, and signal optimization. Their adaptability makes them indispensable in communication systems, industrial control, and measurement instruments.

2. Main Types and Functional Classification

Type	Functional Characteristics	Application Examples
Ceramic Trimmer Capacitors	Compact size, high stability, ceramic dielectric material	Radio transmitters, oscillator circuits
Film Trimmer Capacitors	Low leakage current, polymer film dielectric	Medical equipment calibration
Air Variable Capacitors	Adjustable plate spacing with air dielectric	AM/FM radio tuning circuits
Film Variable Capacitors	Rotary adjustment mechanism, plastic film dielectric	Signal generators, test equipment
Electrolytic Variable Capacitors	Polarized design with liquid/gel electrolyte	Power supply filtering systems

3. Structure and Composition

Typical trimmer capacitors use a ceramic or polymer dielectric sandwiched between metal plates, with a screwdriver-adjustable electrode for capacitance variation. Variable capacitors employ either rotating plate systems (air dielectric) or compressible film stacks. Key components include:

Dielectric material (ceramic, polypropylene, polystyrene)
Movable electrode assembly (rotary/sliding contact)
Calibration scale for precise adjustment
Protective housing (epoxy, plastic, or metal casing)

4. Key Technical Parameters

Parameter	Description	Importance
Capacitance Range	Adjustable capacitance limits (e.g., 1-10 pF)	Determines circuit tuning flexibility
Rated Voltage	Maximum operating voltage (50-200V typical)	Affects reliability and dielectric breakdown resistance
Temperature Coefficient	Capacitance variation per C ( 5 to 100 ppm/ C)	Impacts frequency stability
Adjustment Resolution	Minimum achievable capacitance change	Critical for precision calibration
Mechanical Life	Number of adjustment cycles before failure	Dictates component longevity in dynamic applications

5. Application Fields

Telecommunications: RF filters, antenna matching networks
Consumer Electronics: Radio frequency tuning circuits, audio equalizers
Industrial Control: Sensor calibration, power factor correction
Medical Equipment: Diagnostic imaging device signal conditioning
Automotive: Ignition system tuning, radar calibration

6. Leading Manufacturers and Products

Manufacturer	Product Series	Key Features
KEMET	TR3 Series	Ceramic trimmers with 0.5-12 pF range
AVX	VT Series	Vacuum variable capacitors to 1000 pF
Murata	7WT Series	Sub-miniature trimmers for SMT applications
EPCOS	B4350 Series	High-voltage variable capacitors (2000V rating)

7. Selection Guidelines

Determine required capacitance range and adjustment precision
Evaluate environmental conditions (temperature, vibration, humidity)
Select appropriate dielectric material for stability requirements
Consider packaging type (through-hole vs. surface-mount)
Assess mechanical actuation needs (manual vs. motorized tuning)
Verify voltage rating exceeds circuit requirements

Industry Trends and Future Outlook

The market is shifting toward miniaturization (sub-1mm components), enhanced digital control integration, and improved temperature stability ( 5 ppm/ C specifications becoming standard). Emerging applications in 5G infrastructure and IoT devices are driving demand for ultra-low-loss trimmers. Material innovations like nanoceramic dielectrics and MEMS-based variable capacitors are expected to dominate next-generation designs. Environmental regulations are also pushing manufacturers toward lead-free and RoHS-compliant packaging solutions.