What is a capacitor ?

Discover the basic information about capacitors, to improve your choice



Definition from the dictionnary: « Capacitor »: Device able to accumulate charges and to relaunch them in a very short time. 


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What it really is:

It's an electrical component made of 2 conductive armatures (called electrodes) separated by an isolating layer. Its main property is to store electrical charges on its armatures.

There is a direct link between the voltage put on the capacitor and the value of the charge at the armatures

This coefficient C, the capacitance, is the value caracterizing mathematically the capacitors.

As we can identifie a direct link between U and I in the capacitor we can caracterize it as a dipole this way:

3 main dipoles :

In the physical reality:

  •   Contacts with the PCB (terminations) + Other internal contact suh as the metallic contacts, or the physical internal resistivity of the used materials. → Resistance in the circuit
  •   Other losses due mainly to the leads → inductive effect in the circuit.

Example of possible caracterization:

That’s why the Esr is always written « at a certain frequency »  which should be the resonnance frequency.

This is also why the capacitors have frequency optimal ranges. The higher the resonance frequency is, the higher the frequencies are withstanded by the capacitor.


In terms of energy

Efficient energy is Ec.


In reality E= Ec+Er+Ei with:

Ec = Energy due to the ideal capacitor

Er = Energy to the ESR

Ei = Energy due to the leakage.


So Er and Ei are caracterized by heating (Joule effect).

So even if that’s not always a key paramter, the lower the esr the better it is for the circuit.


If the capacitor is polarized :

If the capacitor is not polarized :

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1) Voltages (V)

2) Capacitance of Capacitor


3) Capacitance / volume

4) Tan Delta / ESR


5) Price of the function

Whatever the function, the price of capacitors is important !

A cheap function does not mean a cheap product:

10 caps at 10€ is less expensive than 1 cap at 50€ … 


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                                        Benefits of capacitors



  • The least expensive
  • The highest energy density
  • Polarized
  • Difficulties in storage
  • High ESR and tan Delta
  • Lowest temperature range



  • Ideal for high frequencies
  • The biggest range of values (CAPA voltage)


  • Highest Price of the functions
  • Low energy density
  • Low values of capacitance


  • Highest ripple curents
  • Highest voltages
  • Lowest ESR and tan Delta
  • Most expensive
  • Lowest energy density
  • High price of the function


  • Lower ESR than aluminum,
  • Good energy density and price of the function
  • Polarized
  • Solid can burn
  • High ESR and tan Delta




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Published on 10 Jan 2022 by Stephane PERES

Exxelia expands its High-Performance Dielectric Resonators and Ferrites capabilities for Microwave Applications

New capabilities include the use of its latest E7000 material, which provides narrow bandwidths, temperature stability and high Q-factor together with advanced manufacturing skills such as the capability to deliver extremely small size, and complex ferrite designs.   Exxelia's E7000 series is a Ba-Mg-Ta based material that combines an ultra-high Q-factor and the possibility to get different temperature coefficients upon request. E7000 features the highest performance requested for space use in the frequency range from 5 to 32 GHz, and guarantees a Qxf up to > 250 000 at 10GHZ. In addition, Exxelia is now able to support the most advanced RF designs with the delivery of complex geometries such as Y-shape ferrites for microwave switches or Toroidal designs for phase shifters applications. Those miniaturized and complex products may be as small as few mm only and benefit from exceptional quality, superior performance and low loss (ΔH) materials. Exxelia is a unique manufacturer producing its own raw materials for Ferrites and Dielectrics with proprietary formulations for use in the most demanding environments.   Nicolas Dabadie, Microwave Materials business development manager at Exxelia said: "We are pleased to support our customers’ more and more complex designs and demanding applications. Our unique capability to master the manufacturing from raw materials to high-end finished products opens the way to new solutions for microwave applications going from few MHz to 40GHz".     E7000 SERIES TECHNICAL SPECIFICATIONS : Dielectric constant : 24 Q x f Factor (GHz) : 250000 Frequency : Min : 5900 MHz / Max : 37150 MHz Custom shapes available : disk, cylinder, square etc… Typical Q factor: 25000 at 10 GHz   More information: https://exxelia.com/en/product/detail/636/e7000   Ferrite materials are used in microwave devices such as isolators, circulators, diplexers, filters and phase shifters. They have dielectric and magnetic properties due to the presence of magnetic ions such as iron within the composition. Exxelia also offers a wide range of dielectric resonators series, including coaxial resonators in different sizes. Please contact us for additional details !


EXXELIA ACQUIRES MICROPEN TECHNOLOGIES CORPORATION AND ADDS RESISTORS TO ITS HIGH-RELIABILITY PASSIVE COMPONENTS PORTFOLIO   Micropen, Technology Leader in the Deisgn, Development and Manufacture of High Precision Resistors and Special Sensors Joins Exxelia  Exxelia Completes its High-Rel Passive Component Portfolio by Adding Resistors to the Existing Capacitors & Magnetic Product Lines and Expands its Offer to Critical Sensors for the Medical & Security markets  Exxelia Strengthens its Footprint in the USA with a Fourth Manufacturing Facility  Micropen Scales its Business Outside the USEA Through Exxelia's Local Presence, Especially in Europe and Asia    PARIS, France and HONEOYE FALLS, NY, USA, January 6th, 2020 – Exxelia, a leading designer and manufacturer of High-Rel passive components and sub-systems dedicated to severe environments, announced that it has completed, on Dec 23rd, 2019, the acquisition of Micropen Technologies Corporation. Micropen is a well-established designer and manufacturer of high technology resistors, known under the Ohmcraft® brand, serving the medical, defense, space and industrial markets. Micropen also manufactures with the same technology unique special sensors dedicated to the medical and security markets. Established in 1982 in Honeoye Falls, NY, Micropen Technologies has developed a unique process to print critical functional materials, such as conductive electrodes, precious metals, on various planar or 3D substrates, such as ceramic, plastic and others. This patented system is the core technology for the design and manufacture of Ohmcraft® complete line of resistors as well as some of the world’s most innovative monitoring & stimulating medical sensors. “We are very excited to welcome Micropen’s talented, engaged and committed team, and very proud to add Micropen’s unique technology under our already extensive portfolio of highly-engineered passive components and sensors. Thanks to this unrivaled process, Exxelia gains a foothold in the high-rel resistors world and enhances its ability to serve as a key product solution provider to customers with mission-critical applications”, said Paul Maisonnier, Chief Executive Officer of Exxelia. According to Ed Petrazzolo, President & Chief Executive Officer of Micropen Technologies, “Micropen is delighted to now be a part of Exxelia's growth and expanded product offerings. The commonalities between our two companies in culture, engineering, technology and manufacturing excellence are outstanding and we are excited by the global reach that Exxelia offers to our Ohmcraft resistors and Micropen printing capabilities”. ### About Micropen Technologies: Micropen Technologies Corporation designs, develops, manufactures and sells a line of custom, high-voltage, high performance thick film resistors and precision electronic components utilizing its proprietary electronic printing system. Micropen’s precision resistor line is marketed under the brand name, Ohmcraft, a recognized leader in custom, high performance resistors for the medical, defense, space, detection and test & measurement markets. The Micropen division is an outsourced product development and manufacturer for the medical device and detection markets. For more Information, visit ohmcraft.com and/or micropen.com About Exxelia: EXXELIA is a leading global designer and manufacturer of high performance passive components and subsystems. Exxelia’s wide products portfolio includes film, tantalum, ceramic and electrolytic capacitors, inductors, transformers, microwave components, position sensors, slip rings and high-precision mechanical parts. Recognized worldwide for its advanced design and technical expertise, EXXELIA develops both “catalog” and “custom” products exclusively serving high-reliability markets such as aerospace, defense, medical, transportation, telecommunication infrastructure and advanced industrial applications. Additional information can be found at https://exxelia.com