10

1k

1M

FREQUENCY (Hz)

-5

5

20

100k

10k

100

15

10

0

VDD = 2.2V

-40°C

25°C

85°C

ABSOLUTE

SOUND

PRESSURE

[dBPa]

-94 dB

SENSITIVITY

[dBV/Pa]

SOUND

PRESSURE

[dB SPL]

VOLTAGE

[dBV]

LMV1012

SNAS194H – NOVEMBER 2002 – REVISED MAY 2013

www.ti.com

Figure 24. dB SPL to dBV Conversion

Example: Busy traffic is 70 dB SPL

VOUT = 70 −94 −44 = −68 dBV

(4)

This is equivalent to 1.13 mVPP

Since the LMV1012-15 has a gain of 6 (15.6 dB) over the JFET, the output voltage of the microphone is 6.78

mVPP. By implementing the LMV1012-15, the sensitivity of the microphone is -28.4 dBV/Pa (−44 + 15.6).

LOW FREQUENCY CUT OFF FILTER

To reduce noise on the output of the microphone a low frequency cut off filter has been implemented. This filter

reduces the effect of wind and handling noise.

It's also helpful to reduce the proximity effect in directional microphones. This effect occurs when the sound

source is very close to the microphone. The lower frequencies are amplified which gives a bass sound. This

amplification can cause an overload, which results in a distortion of the signal.

Figure 25. LMV1012-15 Gain vs. Frequency Over Temperature

The LMV1012 is optimized to be used in audio band applications. By using the LMV1012, the gain response is

flat within the audio band and has linearity and temperature stability (see Figure 25).

12

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