Designing the circuit

AN4598

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DocID026988 Rev 1

R3 and C3 create a low-pass gain so as not to amplify noise beyond the audio bandwidth.

Equation 6.

Equation 6

Figure 3 shows the transfer function of the proposed schematics.

For high frequencies the gain is 1.

In order to remove the input noise beyond the audio frequency, an additional low-pass RC

filter can be used on the OUT node.

Figure 3. Voltage gain vs frequency

Note:

C8 and C9 decoupling capacitors should be placed as close as possible to the op amp and

microphone.

G1

R3

R2

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