Application information

TS472

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5.5

Gain settings

The gain in the application depends mainly on:

●

the sensitivity of the microphone

●

the distance to the microphone

●

the audio level of the sound

●

the desired output level

The sensitivity of the microphone is generally expressed in dB/Pa, referenced to 1V/Pa. For

example, the microphone used in testing had an output voltage of 6.3mV for a sound

pressure of 1 Pa (where Pa is the pressure unit, Pascal). Expressed in dB, the sensitivity is:

20Log(0.0063) = -44 dB/Pa

To facilitate the first approach, Table 11 below gives voltages and gains used with a low cost

omnidirectional electret condenser microphone of -44dB/Pa.

The gain of the TS472 microphone preamplifier can be set:

1.

It allows to adapt more precisely the gain to each application.

2.

provided by TS472 itself on BIAS pin.

Table 11.

Typical TS472 gain vs. distance to the microphone (sensitivity -44dB/Pa)

Distance to microphone

Microphone output voltage

TS472 Gain

1cm

20

20cm

100

Table 12.

Selected gain vs. gain select resistor

Gain (dB)

010

20

30

40

470k

27k

4k7

1k

68

Figure 35. Gain in dB vs. gain select resistor

Figure 36. Gain in V/V vs. gain select resistor

10

100

1k

10k

100k

1M

-10

0

10

20

30

40

50

Tamb=25

R

GS

(

10

100

1k

10k

100k

1M

1

10

100

Tamb=25

R

GS

(