7. A researcher is using a sensitive microphone to record the sounds of insects.

Question

7. A researcher 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?

8. The researcher in Problem 7 finds that the noise has been reduced using the new circuit, but that it is still unacceptably high. She has hooked up the microphone to the op amp circuit using two ordinary copper wires. Name two alternative wiring choices she has that might help eliminate the noise.

Explanation / Answer

7) Differential amplifier can be used to remove much noise as it it will remove commom mode noise from the microphone.

8)Two alternate wiring choices:

a)Two twisted pair using 2 conductors can be used to reduce electromagneic interference..

b)And two twisted pairs can be used using 4 conductors instead of two large connductors can be used to reduce electromagnetic interference.

21 AWG copper wire can be used for wiring instead of ordinary copper wire..

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