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參數(shù)資料
| 型號(hào)： | LMV551MGX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | 3 MHz, Micropower RRO Amplifier |
| 中文描述： | OP-AMP, 4.5 uV OFFSET-MAX, 3 MHz BAND WIDTH, PDSO5 |
| 封裝： | SC-70, 5 PIN |
| 文件頁(yè)數(shù)： | 10/12頁(yè) |
| 文件大小： | 326K |
| 代理商： | LMV551MGX |
In such a case a number of techniques can be used to restore
stability to the circuit. The idea behind all these schemes is to
modify the frequency response such that it can be restored to
an ROC of 20 dB/decade, which ensures stability.
In The Loop Compensation
Figure 2
illustrates a compensation technique, known as ‘in
the loop’ compensation, that employs an RC feedback circuit
within the feedback loop to stabilize a non-inverting amplifier
configuration. A small series resistance, R
, is used to isolate
the amplifier output from the load capacitance, C
, and a small
capacitance, C
, is inserted across the feedback resistor to
bypass C
L
at higher frequencies.
20152604
FIGURE 2. In the Loop Compensation
The values for R
and C
are decided by ensuring that the
zero attributed to C
lies at the same frequency as the pole
attributed to C
. This ensures that the effect of the second
pole on the transfer function is compensated for by the pres-
ence of the zero, and that the ROC is maintained at 20 dB/
decade. For the circuit shown in
Figure 2
the values of R
and
C
are given by
Equation 1
. Values of R
and C
required for
maintaining stability for different values of C
, as well as the
phase margins obtained, are shown in
Table 1
. R
F
, R
IN
, and
R
L
are to be 10 k
, while R
OUT
is 340
.
(1)
TABLE 1.
C
L
(pF)
R
S
(
)
C
F
(pF)
Phase Margin
(°)
47
42
40
50
100
150
340
340
340
8
15
22
Although this methodology provides circuit stability for any
load capacitance, it does so at the price of bandwidth. The
closed loop bandwidth of the circuit is now limited by R
F
and
C
F
.
Compensation By External Resistor
In some applications it is essential to drive a capacitive load
without sacrificing bandwidth. In such a case, in the loop com-
pensation is not viable. A simpler scheme for compensation
is shown in
Figure 3
. A resistor, R
, is placed in series be-
tween the load capacitance and the output. This introduces a
zero in the circuit transfer function, which counteracts the ef-
fect of the pole formed by the load capacitance and ensures
stability. The value of R
ISO
to be used should be decided de-
pending on the size of C
and the level of performance de-
sired. Values ranging from 5
to 50
are usually sufficient to
ensure stability. A larger value of R
will result in a system
with lesser ringing and overshoot, but will also limit the output
swing and the short circuit current of the circuit.
20152612
FIGURE 3. Compensation by Isolation Resistor
Typical Application
ACTIVE FILTERS
With a wide unity gain bandwidth of 3 MHz, low input referred
noise density and a low power supply current, the LMV551/
LMV552 are well suited for low-power filtering applications.
Active filter topologies, such as the Sallen-Key low pass filter
shown in
Figure 4
, are very versatile, and can be used to de-
sign a wide variety of filters (Chebyshev, Butterworth or
Bessel). The Sallen-Key topology, in particular, can be used
to attain a wide range of Q, by using positive feedback to re-
ject the undesired frequency range.
In the circuit shown in
Figure 4
, the two capacitors appear as
open circuits at lower frequencies and the signal is simply
buffered to the output. At high frequencies the capacitors ap-
pear as short circuits and the signal is shunted to ground by
one of the capacitors before it can be amplified. Near the cut-
off frequency, where the impedance of the capacitances is on
the same order as R
and R
, positive feedback through the
other capacitor allows the circuit to attain the desired Q.
20152609
FIGURE 4.
www.national.com
10
L
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMV551MGX/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)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(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV552 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3 MHz, Micropower RRO Amplifier |
| LMV552MM | 制造商:Texas Instruments 功能描述:OP Amp Dual GP R-R O/P 5.5V 8-Pin MSOP T/R 制造商:Texas Instruments 功能描述:OP AMP, RRO, DUAL, 3MHZ, SMD, MSOP8 制造商:Texas Instruments 功能描述:OP AMP, RRO, DUAL, 3MHZ, SMD, MSOP8; Op Amp Type:Low Power; No. of Amplifiers:1; Slew Rate:1V/s; Supply Voltage Range:2.7V to 5.5V; Amplifier Case Style:MSOP; No. of Pins:8; Bandwidth:3MHz; Operating Temperature Min:-40C; Operating;RoHS Compliant: Yes |
| LMV552MM/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)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(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV552MMX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3 MHz, Micropower RRO Amplifier |
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