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參數資料
| 型號： | LMV821M5 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運算放大器 |
| 英文描述： | Low Voltage, Low Power, R-to-R Output, 5 MHz Op Amps |
| 中文描述： | OP-AMP, 3500 uV OFFSET-MAX, 5 MHz BAND WIDTH, PDSO5 |
| 封裝： | SOT-23, 5 PIN |
| 文件頁數： | 14/24頁 |
| 文件大小： | 1068K |
| 代理商： | LMV821M5 |
the pass band gain. Increasing R
by ten percent, increased
the gain by 0.4 dB, while increasing R
5
by ten percent, de-
creased the gain by 0.4 dB.
TABLE 1.
Component (LPF)
R
a
C
1
R
2
R
3
C
3
R
4
R
5
Sensitivity (LPF)
-1.2
-0.1
-1.1
+0.7
-1.5
-0.6
+0.6
Component (HPF)
C
a
R
b
R
1
C
2
R
3
R
4
R
5
Sensitivity (HPF)
-0.7
-1.0
+0.1
-0.1
+0.1
-0.1
+0.1
Active filters are also sensitive to an op amp’s parameters
-Gain and Bandwidth, in particular. The LMV822/24 provide
a large gain and wide bandwidth. And DAAFs make excel-
lent use of these feature specifications.
Single Amplifier versions require a large open-loop to
closed-loop gain ratio - approximately 50 to 1, at the Fc of
the filter response. Figure 12 shows an impressive photo-
graph of a network analyzer measurement (hp3577A). The
measurement was taken from a 300kHz version of Figure
10 At 300 kHz, the open-loop to closed-loop gain ratio
@
Fc
is about 5 to 1. This is 10 times lower than the 50 to 1 “rule
of thumb” for Single Amplifier Active Filters.
In addition to performance, DAAFs are relatively easy to de-
sign and implement. The design equations for the low-pass
and high-pass DAAFs are shown below. The first two equa-
tion calculate the Fc and the circuit Quality Factor (Q) for the
LPF (Figure 10). The second two equations calculate the Fc
and Q for the HPF (Figure 11).
To simplify the design process, certain components are set
equal to each other. Refer to Figure 10and Figure 11 These
equal component values help to simplify the design equa-
tions as follows:
To illustrate the design process/implementation, a 3 kHz,
Butterworth response, low-pass filter DAAF (Figure 10) is
designed as follows:
1. Choose C
1
= C
3
= C = 1 nF
2. Choose R
4
= R
5
= 1 k
3. Calculate R
a
and R
2
for the desired Fc as follows:
4. Calculate R
for the desired Q. The desired Q for a Butter-
worth (Maximally Flat) response is 0.707 (45 degrees into
the s-plane). R
3
calculates as follows:
Notice that R
3
could also be calculated as 0.707 of R
a
or R
2.
The circuit was implemented and its cutoff frequency mea-
sured. The cutoff frequency measured at 2.92 kHz.
The circuit also showed good repeatability. Ten different
LMV822 samples were placed in the circuit. The correspond-
ing change in the cutoff frequency was less than a percent.
DS100128-92
FIGURE 12. 300 kHz, Low-Pass Filter, Butterworth
Response as Measured by the HP3577A Network
Analyzer
www.national.com
14
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LMV821M5/NOPB | 功能描述:運算放大器 - 運放 Low Volt Sgl Op Amp 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 |
| LMV821M5/NOPB | 制造商:Texas Instruments 功能描述:Operational Amplifier (Op-Amp) IC |
| LMV821M5NOPB | 制造商:Texas Instruments 功能描述: |
| LMV821M5X | 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 |
| LMV821M5X/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 |
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