Microphone capsules (electret microphones) contain a transistor called a FET (Field-Effect Transistor), which converts impedance and amplifies signals. This FET requires a DC working voltage, unlike dynamic microphones that generate an electrical signal directly from sound without needing any additional voltage.
The working voltage for electret condenser microphones is typically specified between 1.5V and 9V in datasheets. However, the common practical voltages are around 2V to 3V. While you can choose voltages like 4V, 4.5V, 5V, or even 6V, it is not recommended to use the upper limit values (7V, 8V, or 9V). Higher voltages do not improve the microphone’s sensitivity and may reduce the lifespan of the FET.
In some automotive applications, where the supply voltage is 12V, the voltage is regulated and stepped down to around 7.5V for the microphone in voice-controlled circuits. Although this is within the specified range, it is close to the upper limit, and we do not recommend operating microphones at these high voltages for extended periods, as it can shorten the FET’s lifespan.
We recommend setting the working voltage between 2V and 4.5V for optimal performance. Microphones can still operate below 2V (but above 1V), though performance may suffer, leading to distortion or reduced output. At voltages below 1V, the microphone may not work at all. Regardless of the type of electret microphone, including silicon microphones, the working voltage should not be set too low or too high. Excessive voltage does not increase sensitivity but increases consumption and reduces the FET’s lifespan.
Following these guidelines will ensure your microphone capsules operate efficiently and last longer.
