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參數(shù)資料
| 型號： | LMV794MAX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運(yùn)動控制電子 |
| 英文描述： | 88 MHz, Low Noise, 1.8V CMOS Input, Decompensated Operational Amplifiers |
| 中文描述： | DUAL OP-AMP, 1650 uV OFFSET-MAX, 88 MHz BAND WIDTH, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁數(shù)： | 13/22頁 |
| 文件大小： | 543K |
| 代理商： | LMV794MAX |
20216324
FIGURE 3. Open Loop Gain for Unity-Gain Stable Op Amp
and Decompensated Op Amp
Having a higher frequency for the dominate pole will result in:
1.
The DC open-loop gain (A
VOL
) extending to a higher
frequency.
2.
A wider closed loop bandwidth.
3.
Better slew rate due to reduced compensation
capacitance within the op amp.
The second open loop pole (f
) for the LMV793/LMV794 oc-
curs at 45 MHz. The unity gain (f
’) occurs after the second
pole at 51 MHz. An ideal two pole system would give a phase
margin of 45° at the location of the second pole. The LMV793/
LMV794 have parasitic poles close to the second pole, giving
a phase margin closer to 0°. Therefore it is necessary to op-
erate the LMV793/LMV794 at a closed loop gain of 10 or
higher, or to add external compensation in order to assure
stability.
For the LMV796, the gain bandwidth product occurs at 17
MHz. The curve is constant from f
d
to f
u
which occurs before
the second pole.
For the LMV793/LMV794, the GBW = 88 MHz and is constant
between f
and f
2
. The second pole at f
occurs before A
= 1. Therefore f
u
’ occurs at 51 MHz, well before the GBW
frequency of 88 MHz. For decompensated op amps the unity
gain frequency and the GBW are no longer equal. G
is the
minimum gain for stability and for the LMV793/LMV794 this
is a gain of 10 or 20 dB.
Input Lead-Lag Compensation
The recommended technique which allows the user to com-
pensate the LMV793/LMV794 for stable operation at any gain
is lead-lag compensation. The compensation components
added to the circuit allow the user to shape the feedback
function to make sure there is sufficient phase margin when
the loop gain is as low as 0 dB and still maintain the advan-
tages over the unity gain op amp.
Figure 4
shows the lead-
lag configuration. Only R
C
and C are added for the necessary
compensation.
20216325
FIGURE 4. LMV793 with Lead-Lag Compensation for
Inverting Configuration
To cover how to calculate the compensation network values
it is necessary to introduce the term called the feedback factor
or F. The feedback factor F is the feedback voltage V
-V
B
across the op amp input terminals relative to the op amp out-
put voltage V
OUT
.
From feedback theory the classic form of the feedback equa-
tion for op amps is:
A is the open loop gain of the amplifier and AF is the loop gain.
Both are highly important in analyzing op amps. Normally AF
>>1 and so the above equation reduces to:
Deriving the equations for the lead-lag compensation is be-
yond the scope of this datasheet. The derivation is based on
the feedback equations that have just been covered. The in-
verse of feedback factor for the circuit in
Figure 4
is:
(1)
where 1/F's pole is located at
(2)
1/F's zero is located at
(3)
(4)
13
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| LMV794MAX/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 |
| LMV794MM | 制造商:Texas Instruments 功能描述:OP Amp Single GP R-R O/P 5.5V 8-Pin MSOP T/R |
| LMV794MM/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 |
| LMV794MMX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:88 MHz, Low Noise, 1.8V CMOS Input, Decompensated Operational Amplifiers |
| LMV794MMX/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 |
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