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 Ohmcraft Custom Resistors Enable Metabolic Analyses of Live Cell Cultures in Pharmaceutical Research

To do so, they must rely on life science research and diagnostic instruments with complex high gain amplifier circuits. Leading manufacturers of this type of equipment have partnered with Exxelia Ohmcraft to design custom, high-resistance surface mount resistors that are essential to the function of these circuits. Specifically, oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) are two key indicators of mitochondrial respiration and glycolysis that provide a systems-level view of cellular metabolic function in cultured cells. The analyzer equipment conducts these measurements automatically. “The accuracy and reliability of these tools are crucial to the researchers’ ability to make progress in their studies, which have the potential to change—and save—lives,” said Eric Van Wormer, Vice President of Exxelia Ohmcraft. “To meet the design needs of this particular application, we developed a custom resistor solution with a unique form factor and used special terminations to facilitate the manufacturability of the end product.” Exxelia Ohmcraft’s technology utilizes the proprietary Micropen electronic printing system to “print” precise, narrow, serpentine lines with resistive ink on a ceramic substrate, producing higher performance resistors over a wider range of values on a smaller surface area than is possible with conventional film resistor technology.

Introducing new EXXELIA.COM

Completely re-designed Exxelia new website features user-friendly design, improved functionalities and enhanced rich content to assist electronic engineers, component purchasers, industry professionals and students to quickly access information.  Created with the user experience firmly in mind, the website has been designed to make Exxelia’s vast product portfolio easy to browse. A parametric search engine with filters specific to each product category (capacitance, voltage, temperature, insertion loss, current, frequency, etc.) enables to narrow down the product portfolio and access information in a quick, trouble free and efficient way. More than 680 product series are listed on the website with relevant literature accessible for each series: datasheets, 3D models, high-res pictures and much more.      Technical data, application guides, white papers work together to provide a detailed overview of Exxelia’s capabilities across wide range of technologies. An application section presents the major markets the group is involved in, with a dedicated product selection for every sub-environments: avionics & cockpit, actuation systems, satellites, radars, medical imaging, etc. This section also contributes to better present Exxelia’s diversified offer of components that includes capacitors, magnetics, filters and electromechanical solutions.  “We are thrilled about the new website launch and the robust information it provides to better understand Exxelia wide product offering. We believe this will improve the overall customer experience and strengthen our brand as a technology leader and quality product manufacturer” said Marie Evrard, Head of Marketing and Communication at Exxelia.  “We believe this new site will allow our visitors to have a very informative experience as we increase our market presence. The group continues to grow and it was necessary to streamline our website to make it easier to navigate.” states Jérôme Tabourel, Marketing & Sales VP at Exxelia. Exxelia new website will be updated on a regular basis with new product launches, company info, events and technical information.