8.3.1 Two-Wire Electret Microphone Preamplifier

The circuit in Figure 60 can be modified to accommodate two-wire electret microphones, as shown in Figure 62. In two-wire configurations, there is no resistor in series with the source of the internal JFET of the microphone. The audio signal is output as a varying voltage across the biasing resistor (2.2 kΩ in Figure 62) of the capsule. The preamplifier input is AC-coupled to the biasing resistor through a 0.1-µF capacitor and 47-kΩ input resistor.

Figure 62. Two-Wire Electret Microphone Preamplifier