TS472

Application information

Doc ID 11015 Rev 6

15/25

4.5

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 1 V/Pa. For

example, the microphone used in testing had an output voltage of 6.3 mV 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 10 gives voltages and gains used with a low-cost omni-

directional electret condenser microphone of -44 dB/Pa.

The gain of the TS472 microphone preamplifier can be set as follows.

1.

From -1.5 dB to 41 dB by connecting an external grounded resistor RGS to the GS pin.

This enables the gain to be adapted more precisely to each application.

2.

To 20 dB by applying VGS > 1VDC on the gain select (GS) pin. This setting can help to

reduce a number of external components in an application, because 2.0 VDC is

provided by the TS472 itself on the BIAS pin.

Table 10.

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

Distance to microphone

Microphone output voltage

TS472 gain

1cm

30mVRMS

20

20 cm

3 mVRMS

100

Table 11.

Selected gain vs. gain select resistor

Gain (dB)

010

20

30

40

RGS (Ω)

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

°C

R

GS

(Ω)

10

100

1k

10k

100k

1M

1

10

100

Tamb=25

°C

R

GS

(Ω)