8.3.1 Preamplifier for Professional Microphones

Figure 60 shows a preamplifier designed for high performance applications that require low-noise and high common-mode rejection. Both channels of the INA1620 are configured as a two-op amp instrumentation amplifier with a variable gain from 6 to 40 dB. The excellent matching of the integrated 1kΩ resistors allows for high common-mode rejection in the circuit. An OPA197 is configured as a buffered power supply divider to provide a biasing voltage to the circuit, allowing the system to operate properly on a single 9-V battery. The additional components at the INA1620 inputs are for phantom power, EMI, and ESD protection.

Figure 60. Preamplifier for Professional Microphones