Der Blätterkatalog benötigt Javascript.
Bitte aktivieren Sie Javascript in Ihren Browser-Einstellungen.
The Blätterkatalog requires Javascript.
Please activate Javascript in your browser settings.
Knowhow 10 1 2021 Powered by Committed to Excellence www rutronik com Circuits for miniature loudspeakers Small speakers big sound Rrrring Rrrringwhen every telephone still had a cable that was exactly how a phone call would sound Dingdong was how the doorbell would herald the arrival of house visitors Today users have a choice of countless songs sounds and natural noises Miniature loudspeakers with wide frequency ranges make this possible Audible communication in the form of speech or music is becoming increasingly important in humanmachine interfaces HMI and this is also true of industrial applications In this field audible signals or announcements can supplement visual indications especially when information needs to be conveyed despite a lack of visual contact with the device There is a selection of several loudspeaker types for a wide variety of applications Aconventional loudspeaker also known as a dynamic or magnetic loudspeaker basically consists of a permanent magnet mounted on a voice coil These in turn are connected at multiple points This structure is surrounded by a loudspeaker frame which supports a taut diaphragm made of paper fabric or plastic Electrical signals DC create a magnetic field in the coil which causes the diaphragm to oscillate These oscillations create the acoustic signals perceived by the human ear The physics of this type of loudspeakerin particular sound pressure levels SPL require a certain geometry This often makes the loudspeaker a limiting factor that prevents the device from being thinner Piezoelectric speakers Piezoelectric speakers on the other hand are available in thin forms They do not require a voice coil to generate soundinstead they use the piezoelectric effect whereby the tried and true piezoelectric ceramic material is usually bonded to a brass or nickel plate and made to vibrate by supplying it with a voltage Unlike dynamic loudspeakers which measure at least four millimeters in height these are a single millimeter tall at most Another design is that of the multilayer piezo loudspeaker They are constructed not just from one ceramic element but multiple layers with each layer filtering different frequency spectrums This allows them to generate superior audio The PiezoListen from TDK is among the thinnest speakers in the world Measuring just 0 49 mm in height it can be glued easily to smooth surfaces which are then made to oscillate This is how it transforms practically any surface into a loudspeaker be it a display a table a mirror or the plastic housing of an application The PiezoListen generates a high sound level pressure even at low voltages of 24 Vpp or less Multilayer piezo loudspeakers are triggered and controlled in exactly the same way as a dynamic loudspeaker with an IC amplifier Amplifier circuits Amplifier circuits for loudspeakers need to consider three factors in particular the shortterm power the impedance and the frequency range The shortterm powerthe load that a loudspeaker can briefly withstand from an amplifier signal without being damagedcan range from several 100 mW to several watts in miniature speakers By Jochen Neller Technical Support and Anne Santhakumar Product Sales Manager Acoustic Components & Timing Devices both at Rutronik Construction of a dynamic loudspeaker Figure PUI Audio Figure PUI Audio Traditional structure of a ceramic loudspeaker