What is an electret microphone

Microphones - devices that enhance sound volume are ubiquitous. Among their varieties there are professional as well as simpler options for home use. In addition, microphones are condenser and electret type.

What is an electret microphone

To better understand what kind of device it is, you must first clarify what an electret is.

An electret is a special material that can be polarized for a rather long time. In addition, he has the property of creating an electromagnetic field.

Conventional condenser microphones have a rather low impedance, and in the electret version, it is much higher. Therefore, such devices require connection to amplifiers that have a fairly high resistance. They also need an external power supply.

An amplifier is located in its body and all the voltage supplied to the device is required for its power supply. In capacitor options, it goes to charge.

The device consists of capacitors in which some of the plates are made of film. This film is pulled onto the ring. Further, it is exposed to charged particles. Electrons penetrate into it to a shallow depth. As a result of this, a charge is created in the space around them. This charge can exist for quite a long time.

On top of the film is covered with a layer of metal. It is also used as an electrode. At a small distance from it is another electrode - a small metal cylinder. With its flat side, it is turned to the film.

The polyethylene membrane creates sound vibrations transmitted to the electrodes, resulting in the generation of current. The current strength is extremely small, while the output impedance is high. Therefore, the transmission of audio is quite difficult. In order for the small current strength and high resistance to be matched, a special cascade is used. It is performed in the form of a unipolar transistor, and is located in the device’s body, in a special capsule.

The principle of operation of the electret device is based on the ability of certain types of materials to change their surface charge under the influence of an acoustic wave. In this case, the materials must have a very high dielectric constant.

REFERENCE! Since these devices have a very high output impedance, they can be easily connected to receivers and amplifiers with incoming high impedance. To make sure that this particular amplifier can be used, you need to connect a multimeter to it and see the received values. If, as a result of measurements, the multimeter showed values ​​equal to 2-3 Volts, then this amplifier can be connected to an electret microphone.

Now almost all equipment can work with this type of device.

Electret microphones have almost replaced other options. This is due to the fact that they have a reasonable price, but at the same time they are reliable in operation. Another plus is their small size and weight.