Microphone preamplifier with phantom power using INA103

As shown in the figure, this is a microphone preamplifier with phantom power. When the "phantom power" switch is connected to 48V, a 48V DC voltage is provided to the microphone; when it is connected to 47kΩ, a 0V DC voltage is provided to the microphone. Two 20dB attenuation linkage switches control whether the input signal is attenuated by 20dB (i.e., whether the voltage is divided). The 1kΩ "gain adjustment" potentiometer can adjust the amplifier gain to change the output signal size. The OPA627 forms an output offset voltage control loop to control the offset voltage of the output stage A3.