What is a capacitor ?

Discover the basic information about capacitors, to improve your choice


▲ WHAT IS A CAPACITOR ?

 

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

 

See our capacitors in catalog 

 

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 :

See our capacitors in catalog

 

▲ MAIN CARACTERISTICS

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€ … 

 

See our capacitors in catalog

 

▲ FINAL OVERVIEW

  Technology

                                        Benefits of capacitors

                         Constrains

 Aluminum

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

 Ceramic

 

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

 

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

 Film

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

 Tantalum

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

 

 

 

See our capacitors in catalog

Published on 10 Jan 2022 by Stephane PERES

EuMW 2017 - booth# 190

Ultra low ESR, high RF power and high self-resonant frequency The NHB series is a complete range of MLCC based on NPO dielectric material providing a very high Self Resonant Frequency and limiting the parasite Parallel Resonant Frequencies. The series is available in 1111 size with capacitance ranging from 0. 3pF to 100pF. NHB series offers excellent performance for RF power applications at high temperature up to 175°C @ 500 VDC. The lowest ESR is obtained by combining highly conductive metal electrodes and proprietary of the NPO low loss rugged dielectrics. NHB series is particularly fit for high power and high frequency applications such as: cellular base station equipment, broadband wireless service, point to point / multipoint radios and broadcasting equipment. Typical circuit applications: impedance matching, bypass, feedback, tuning, coupling and DC blocking.   100% invar tuning screws with self-locking system   Invar-36 is a unique Iron-Nickel alloy (64 % Fe / 36 % Ni) sought-after for its very low coefficient of thermal expansion. With 1.1 ppm. K–1 between 0°C and 100°C, Invar-36 is about 17 times more stable than Brass which is the most traditional and common alloy Tuning Elements are made of. The working temperature range in Space is so wide that this property becomes essential for a reliable and stable cavity filter tuning. Self-locking system is a technology commonly used on Tuning Element made of Brass or other soft “easy-to-machine” alloys but is innovative and pretty advanced when applied to hard and tough Invar 36. The design consists of two threaded segments separated by two parallel slots. After cutting both parallel slots, the rotor is compressed in its length in order to create a plastic deformation. Thus, an offset is induced between the two threaded segments which generates a constant tensile stress in the rotor from the moment threaded segments are screwed. High Q Factor Dielectric Resonators Dielectric resonators are designed to replace resonant cavities in microwave functions such as filters and oscillators. Exxelia has developed with support of ESA and CNES, a new high-end dielectric material, E7000 series, designed for high-end filters where high Q factor is requested. E7000 is Ba-Mg-Ta materials based that combines an ultra-high Q factor and the possibility to get all the temperature coefficients upon request. E7000 provides high-performance requested for space use in the frequency range 5 to 32 GHz, and guarantees up to Qxf > 250 000 at 10GHZ. Typical applications: Satellite multiplexing filter devices, radio links for communication systems (LMDS), military radars.