How to replace speakers with piezoelectric diaphragms: The loudspeaker is large and heavy, so it is not suitable for making small toys in some occasions. piezoelectric plate has the advantages of small volume, light weight and much cheaper price than the loudspeaker. It is practical and suitable in some small toys, electric clocks and other self ringing electronic devices. Piezoelectric Disk is a capacitive element. The ordinary loudspeaker has long inductance in the circuit. It can make sound through current, and DC can also pass through it. If the piezo disc is used to replace the loudspeaker directly, the DC circuit of the amplifier may be interrupted and cannot work in some cases. At this time, we can connect a suitable inductor in parallel at both ends of the piezo disk to make it have a large impedance to the audio, but the amplifier can not work normally, and the electric piezo ceramic element can also sound normally. You can also use the input transformer of an ordinary pocket radio, use its primary as the load of the amplifier, and connect the times (if the secondary is double winding, they can be connected in series) with both ends of the piezo UNIMORPH, which can increase the volume of the piezo diaphragm。