Piezoelectric audio amplifier

A piezoelectric audio amplifier (PAA) is a single integrated circuit or a PCB developed to amplify small audio signals to drive piezoelectric audio loudspeaker elements. A piezo audio amplifier can amplify a small signal sine wave of 1 volt peak-to-peak to a signal of about 30 or 60 volts.
Characteristics
* Max Vpp: Maximum voltage peak to peak that the amplifier can deliver at its output channel.
* Max Cap: Maximum capacitance that the Piezo Audio Amplifier can handle.
The main impedance of the piezo speaker or piezo vibration element is a capacitance with values between 10nF and 1uF.
Basic topology
The construction of a piezo audio amplifier consists out of two basic electronic concepts.
1) A DC-DC converter that creates a specific voltage level for the end amplifier
2) Audio Amplifier Topology: class AB, class D, Class G,….topology for amplifying a small signal. The Maximum voltage level is created by the DC-DC converter.
Common technique
To avoid high voltage levels the Bridge-Tied Load configuration is common used.
An audio signal of 60 volt peak-to-peak (Vpp) can be created with a DC voltage of 30V.
Creating a voltage level of 30Vdc instead of 60Vdc is easier done with a DC-DC converter.
The piezoelectric speaker is between two amplifiers. The left side will see a 30Vpp signal while on the right the same signal of 30Vpp will appear reversed (180°phase shifted).
With this technique the piezo speaker will see a total audio signal of 60Vpp.
e.g. [http://www.sonitron.be/site/epag.php?primid&hid&subid&eid29 PAA-StepUpBTL-01]

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