Therefore, the volume variation of the capacitor will also be more important as the signal amplitude (lVmax – Vminl) increases, leading to higher SPL (Figure 3). If an alternative voltage is applied across a MLCC’s terminals, the capacitor will contract and expand at the frequency of the signal, with a deformation amplitude depending on several factors.īasically, the higher the absolute voltage, the more important the capacitor expansion will be. The influence of the frequency will not be taken into account in the rest of this article. In other words, for the same SPL, a sound with a frequency of 3 kHz will appear louder to our ear than a sound with a lower frequency like 50 Hz. The human ear can peak response around 2.5 kHz to 3 kHz (Figure 2) and has relatively low response at low frequencies. The response of the ear to sound is dependent on the frequency of the sound. In others, the reader’s skills will be roped in. In most cases, common sense can explain the reasons of the “noise”. All the following numerical results are not meant to provide absolute data but rather to be used for relative comparison to each other in order to understand the different influencing factors of the audible noise in MLCCs.Īll reasons for such “noise” are not entirely understood yet and this article mostly exposes facts while not trying to explain why such a parameter produces such an action. The measurement results have been acquired using a highly sensitive Se Electronics 1000A microphone and analyzed with the Spectro Frequency Analyzer 2.0 software. 1: MLCC Deformation Under Electric Field Influence If the dielectric is now subjected to a varying electric field intensity that operates at a frequency which is located in the audible frequency range of the human ear (20 Hz – 20 kHz), the capacitor produces noise, the so called audible noise.įig. However like all ferroelectric dielectrics, it is affected by the piezoelectric effect: certain materials generate an electric potential or electric field on the surface by mechanical deformation. lower aging and a high reliability of its dielectric.
Piezo effect series#
a very low Equivalent Series Inductance (ESL), a small size,.a very low Equivalent Series Resistance (ESR),.MLCCs (Multi Layer Ceramic Capacitor) show numerous advantages compared to commonly used Tantalum Electrolytic Capacitors which include: With the increasing popularity of MLCCs (or ceramic capacitors) in electronic circuits due to their low cost and low profile, their inherent piezoelectric effect exhibiting audible noise can become a problem as more and more electronic devices tend to be handheld.
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