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參數資料
| 型號： | LMV794MM |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運動控制電子 |
| 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： | MSOP-8 |
| 文件頁數： | 15/22頁 |
| 文件大?。?/td> | 543K |
| 代理商： | LMV794MM |
20216303
FIGURE 6. First Try at Compensation, Gain = 1
20216307
FIGURE 7. C Increased to 2.2 nF, Gain = 1
Some over-compensation appears to be needed for the de-
sired overshoot characteristics. Instead of intersecting the
A
curve at 18 dB, 2 dB of over-compensation will be used,
and the A
curve will be intersected at 20 dB. Using
Equa-
tion 5
for 20 dB, or 10 V/V, the closest standard value of R
C
is 240
. The following two waveforms show the new resistor
value with C = 390 pF and 2.2 nF.
Figure 9
shows the final
compensation and a very good response for the 1 MHz
square wave.
20216308
FIGURE 8. R
C
= 240
and C = 390 pF, Gain = 1
20216310
FIGURE 9. R
C
= 240
and C = 2.2 nF, Gain = 1
To summarize, the following steps were taken to compensate
the LMV793 for a gain of 1:
1.
Values for R
and C were calculated from the Bodie plot
to give an expected phase margin of 45°. The values
were based on R
= R
= 2 k
. These calculations gave
R
c
= 330
and C = 390 pF.
2.
To reduce the ringing C was increased to 2.2 nF which
moved the pole of F, the feedback factor, farther away
from the A
VOL
curve.
3.
There was still too much ringing so 2 dB of over-
compensation was added to F. This was done by
decreasing R
C
to 240
.
The LMV796 is the fully compensated part which is compa-
rable to the LMV793. Using the LMV796 in the same setup,
but removing the compensation network, provide the re-
sponse shown in
Figure 10
.
20216321
FIGURE 10. LMV796 Response
For large signal response the rise and fall times are dominat-
ed by the slew rate of the op amps. Even though both parts
are quite similar the LMV793 will give rise and fall times about
2.5 times faster than the LMV796. This is possible because
the LMV793 is a decompensated op amp and even though it
is being used at a gain of 1, the speed is preserved by using
a good technique for external compensation.
15
www.national.com
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LMV794MM/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 |
| 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 |
| LMV796 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:17 MHz, Low Noise, CMOS Input, 1.8V Operational Amplifiers |
| LMV796MF | 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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