Electret microphones and circuits are connected in two ways: source output and drain output. The source output is similar to the emitter output of the transistor.
Three leads are required. Drain D is connected to the positive pole of the power supply. A resistance Rs is connected between the source S and the Ground to provide a source voltage. The signal is output by the source through the capacitance C. The braided wire ground plays a shielding role. The output impedance of the source is less than 2k, the circuit is relatively stable and the dynamic range is large. However, the output signal is smaller than the drain output. The drain output is similar to the common emitter of the crystal triode. Only two leads are required. The drain D is connected to the positive pole of the power supply with a drain resistance RD, the signal is output by drain D through capacitor C. The source S is grounded together with the braid. The drain output has a voltage gain, so the sensitivity of the microphone is higher than that of the source output, but the dynamic range of the circuit is slightly smaller.
The size of Rs and RD depends on the power supply voltage. Generally, it can be selected between 2.2~5.1k. For example, when the power supply voltage is 6V, Rs is 4.7k and RD is 2. 2k. Finally ,we have to point out that no matter the source output or drain output, the electret microphone must provide DC voltage to work ,because it is internally equipped with FET.
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About Us
Guangdong Huaze Acoustics Technology Co., Ltd. , established in Dec 2019, located in Dongguan, is a high-tech enterprise which aims at developing and producing auto acoustics products.
