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Freebase(5.00 / 1 vote)Rate this definition: Electret. Electret is a dielectric material that has a quasi-permanent electric charge or dipole polarisation. An electret generates internal and external electric fields, and is the electrostatic equivalent of a permanent magnet. Oliver Heaviside coined this term in 1885.
A typical electret microphone preamp circuit uses an FET in a common source configuration. The two-terminal electret capsule contains a FET which must be externally powered by supply voltage V + . The resistor sets the gain and output impedance. The audio signal appears at the output, after a DC-blocking capacitor. An electret microphone is a type of electrostatic capacitor-based microphone, which eliminates the need for a polarizing power supply by using a permanently charged material.