Electret Microphones: Advantages and Disadvantages

This page covers the advantages and disadvantages of electret microphones, along with their basic principles. It details the benefits and drawbacks of electret microphones, which operate on the same fundamental principle as condenser microphones.

Basics of Condenser Microphones

Condenser microphones consist of two thin plates forming a capacitor. One plate is flexible, while the other is rigid. In this microphone type, equal and opposite charges are applied to the plates. When sound pressure is applied, the capacitance between the plates varies accordingly. If the charge on the plates is kept constant as the capacitance fluctuates, the voltage across it fluctuates.

What is an Electret Microphone?

Introduction: Electret microphones operate on the same principle as condenser microphones. However, their plates are made of ferroelectric material, which allows them to retain an electric charge similar to how iron retains magnetic polarization.

Electret microphones are commonly used in laptops and portable phones, making up approximately 90% of microphones in use today.

Electret Microphone

The figure above depicts a basic circuit of an electret microphone. It generates a very small amount of current, hence the necessity of a transistor or operational amplifier to boost the signal.

The term “Electret” is derived from “Electrostatic” and “magnet”. These microphones are available with leads attached and with solder pads for surface mount applications.

Advantages of Electret Microphones

Here are the benefits of using electret microphones:

• Inexpensive: They are a relatively inexpensive microphone type.
• Good Quality: Recent electret microphones offer good quality, comparable to condenser microphones.
• Wide Frequency Response: They are suitable for an extremely wide frequency response.
• Suitable for Voice Recording: They are ideal for voice recording, especially for interviews.
• No Polarizing Power Supply Needed: They eliminate the need for a polarizing power supply by using a permanently charged material.

Disadvantages of Electret Microphones

Here are the drawbacks of using electret microphones:

• Requires External Components: They require external components such as a transistor or op-amp to boost the small current signal they produce. Usually, these components are integrated on the same chip.
• Less Sturdy: They are less sturdy compared to dynamic microphones.
• Membrane Wear: The vibrating membrane may wear out within a couple of years.
• Fragile Overall: They are more fragile overall compared to dynamic microphones.
• Poor Quality Cheap Versions: Cheap versions of these microphones often offer poor quality and low sensitivity.
• Unsatisfactory Bass Range: Some users find the bass range to be unsatisfactory.