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參數(shù)資料
| 型號： | LMV1032UP-25 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | Amplifiers for 3 Wire Analog Electret Microphones |
| 中文描述： | 1 CHANNEL, AUDIO AMPLIFIER, PBGA4 |
| 封裝： | ROHS COMPLIANT, MO-211CA, MICRO, SMD-4 |
| 文件頁數(shù)： | 9/11頁 |
| 文件大?。?/td> | 406K |
| 代理商： | LMV1032UP-25 |
Application Section
(Continued)
The conversion is given by:
dBPa = dB SPL + 20*log 20 μPa
dBPa = dB SPL - 94 dB
Translation from absolute sound pressure level to a voltage
is specified by the sensitivity of the microphone. A conven-
tional microphone has a sensitivity of 44 dBV/Pa.
Example: Busy traffic is 70 dB SPL
V
OUT
= 70 94 44 = 68 dBV
This is equivalent to 1.13 mV
PP
Since the LMV1032-06 has a gain of 2 (6 dB) over the JFET,
the output voltage of the microphone is 2.26 mV
. By
implementing the LMV1032-06, the sensitivity of the micro-
phone is 38 dBV/Pa (44 + 6).
LOW FREQUENCY CUT OFF FILTER
To reduce noise on the output of the microphone a low cut
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.
The LMV1032 is optimized to be used in audio band appli-
cations. By using the LMV1032, the gain response is flat
within the audio band and has the linearity and temperature
stability.
ADVANTAGE OF THREE PINS
The LMV1032 has three pins instead of two pins as in the
case of a JFET solution. The third pin brings the advantage
of a low supply current, high PSRR and eliminates the need
for additional components.
Noise pick-up by a microphone in a cell phone is a well-
known problem. A conventional JFET circuit is sensitive for
noise pick-up because of its high output impedance. The
output impedance is usually around 2.2 k
. By separating
the output pin and the positive supply pin a much lower
output impedance is achieved. The output of the LMV1032 is
therefore less sensitive to noise pick-up.
RF noise is amongst other caused by non-linear behavior.
The non-linear behavior of the amplifier at high frequencies,
well above the usable bandwidth of the device, causes AM-
demodulation of high frequency signals. The AM modulation
contained in such signals folds back into the audio band,
thereby disturbing the intended microphone signal. The
GSM signal of a cell phone is such an AM-modulated signal.
The modulation frequency of 216 Hz and its harmonics can
be observed in the audio band. This kind of noise is called
bumblebee noise.
20084211
FIGURE 4. dB SPL to dBV Conversion
20084212
FIGURE 5. Gain vs. Frequency Over Temperature
L
www.national.com
9
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMV1032UP-25/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LMV1032UPX-06 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Amplifiers for 3 Wire Analog Electret Microphones |
| LMV1032UPX-06/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LMV1032UPX-15 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Amplifiers for 3 Wire Analog Electret Microphones |
| LMV1032UPX-15/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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