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參數資料
| 型號： | LMV844MT |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運動控制電子 |
| 英文描述： | CMOS Input, RRIO, Wide Supply Range Operational Amplifiers |
| 中文描述： | QUAD OP-AMP, 800 uV OFFSET-MAX, 4.5 MHz BAND WIDTH, PDSO14 |
| 封裝： | TSSOP-14 |
| 文件頁數： | 13/18頁 |
| 文件大?。?/td> | 419K |
| 代理商： | LMV844MT |
However, using low resistor values will increase the power
consumption of the application. This is not always acceptable
for portable applications.
To determine if the noise is acceptable for the application, use
the following formula for resistor noise :
where:
e
th
= Thermal noise voltage (Vrms)
k = Boltzmann constant (1.38 x 10–23 J/K)
T = Absolute temperature (K)
R = Resistance (
Ω)
B = Noise bandwidth (Hz), fmax - fmin
Given in an example with a resistor of 1M
at 25°C (298 K)
over a frequency range of 100 kHz:
To keep the noise of the application low it might be necessary
to decrease the resistors to 100k, which will decrease the
noise to –97.8 dBV (12.8 uV).
The op amp's input-referred noise of 20 nV/
equivalent to the noise of a 24 k
Ω
resistor.
at 1 kHz is
ACTIVE FILTER
The rail-to-rail input and output of the LMV841/LMV844 and
the wide supply voltage range make these amplifiers ideal to
use in numerous applications. One of the typical applications
is an active filter as shown in
Figure 3
. This example is a band-
pass filter, for which the pass band is widened. This is
achieved by cascading two band-pass filters, with slightly dif-
ferent center frequencies.
20168358
FIGURE 3. Active Filter
The center frequency of the separate band-pass filters can be
calculated by:
In this example a filter was designed with its pass band at 10
kHz. The two separate band-pass filters are designed to have
a center frequency of approximately 10% from the frequency
of the total filter:
C = 33 nF
R1 = 2 k
Ω
R2 = 6.2 k
Ω
R3 = 45
Ω
This will give for filter A:
And for filter B with C = 27 nF:
Bandwidth can be calculated by:
For filter A this will give
and for filter B:
The response of the two filters and the combined filter is
shown in
Figure 4
.
20168359
FIGURE 4. Active Filter Curve
13
www.national.com
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LMV844MT/NOPB | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV844MTX | 制造商:Texas Instruments 功能描述:OP Amp Quad GP R-R I/O 12V 14-Pin TSSOP T/R |
| LMV844MTX/NOPB | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV844Q | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:CMOS Input, RRIO, Wide Supply Range Operational Amplifiers |
| LMV844QMA | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:CMOS Input, RRIO, Wide Supply Range Operational Amplifiers |
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