A student is using a sensitive microphone to record the soun

A student is using a sensitive microphone to record the sounds of insects. The voltage from the microphone is very small (microvolts). She amplifies the microphone\'s signal using an ordinary inverting op amp. She finds that the output signal is contaminated by hum and other noise. What op amp circuit can she use instead of the inverting circuit to eliminate much of the noise?

Solution

Answer:

Use a differential input amplifier to remove all of the common mode noise from the microphone and cables. This differential stage can also have some gain, but its usually best to keep its gain low to maximize common mode suppression, and then follow with an inverting high-gain stage such as she originally used.