Piezoelectric Speakers

Hi all,

Has anyone ever dealt with piezoelectric speakers? I was reading an article and it mentioned using Class D amplifiers to drive the speakers. I thought that piezo speakers relied more on overall voltage swing to produce instead of the actual current draw to drive the speaker. How does a Class D amplifier provide more "oomphf" to a piezo speaker?


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It doesn't. It just wastes less "oomphf" inside itself than a class A or AB or B amp does. At the speaker, they've got the same oomphf.

The class of the amp isn't related to the speaker technology, except to the extent that the speaker has to make sound when presented with the electron faeries from the output amp. ;-)

Hope This Helps! Rich

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Rich Grise

Thanks, Rich! :-)

After reading National's text on piezo speaker technology, I was just a bit curious why a class D would be used to provide the voltage swing that the speaker needs. From my basic understanding of class D, there is a comparator hook up to two MOSFET connected together. The class D text also stated that the voltage drop at the output when one of the MOSFET is on should be zero or close to the bias voltage. I was actually expecting more of a bridge tied load amplifier to provide the high voltage peak to peak to produce a louder sound.

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I recall many years ago when "digital audio" was the latest craze, that some people were talking about making honest-to-god digital speakers (not "digital-ready"). One idea was to have have the speaker integrate the pulse-width-modulated amp output, with the inertia of the speaker providing the integration... perfect for class D. I don't see how piezos would have any advantage here though.

The wilder idea was to have arrays of little on-off transducers that could be driven with binary weighting to produce the desired overall displacement. Piezo might be a good match for this, but not class D... in fact, the amp would just be one power switch for each digital bit. I guess you would have needed 16-channel speaker cables. (Now THERE'S a concept that the Monster Cable people would love!)

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

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Bob Masta

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