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參數(shù)資料
| 型號： | LMV794MA |
| 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： | SOIC-8 |
| 文件頁數(shù)： | 17/22頁 |
| 文件大小： | 543K |
| 代理商： | LMV794MA |
20216389
FIGURE 15. LMV796 Response Gain = +1
With no increase in power consumption the decompensated
op amp offers faster speed over the compensated equivalent
part. These examples used R
= 2 k
. This value is high
enough to be easily driven by the LMV793/LMV794, yet small
enough to minimize the effects from the parasitic capacitance
of both the PCB and the op amp.
Note:
When using the LMV793/LMV794, proper high fre-
quency PCB layout must be followed. The GBW of these parts
is 88 MHz, making the PCB layout significantly more critical
than when using the compensated counterparts which have
a GBW of 17 MHz.
TRANSIMPEDANCE AMPLIFIER
An excellent application for either the LMV793 or the LMV794
is as a transimpedance amplifier. With a GBW product of 88
MHz these parts are ideal for high speed data transmission
by light. The circuit shown on the front page of the datasheet
is the circuit used to test the LMV793/LMV794 as tran-
simpedance amplifiers. The only change is that VB is tied to
the V
CC
of the part, thus the direction of the diode is reversed
from the circuit shown on the front page.
Very high speed components were used in testing to check
the limits of the LMV793/LMV794 in a transimpedance con-
figuration. The photo diode part number is PIN-HR040 from
OSI Optoelectronics. The diode capacitance for this part is
only about 7 pF for the 2.5V bias used (V
to virtual ground).
The rise time for this diode is 1 nsec. A laser diode was used
for the light source. Laser diodes have on and off times under
5 nsec. The speed of the selected optical components al-
lowed an accurate evaluation of the LMV793 as a tran-
simpedance amplifier. Nationals Evaluation Board for decom-
pensated op amps, PN 551013271-001 A, was used and only
minor modifications were necessary and no traces had to be
cut.
20216361
FIGURE 16. Transimpedance Amplifier
Figure 16
is the complete schematic for a transimpedance
amplifier. Only the supply bypass capacitors are not shown.
C
represents the photo diode capacitance which is given on
its datasheet. C
is the input common mode capacitance of
the op amp and, for the LMV793 it is shown in the last drawing
of the Typical Performance Characteristics section of this
datasheet. In
Figure 16
the inverting input pin of the LMV793
is kept at virtual ground. Even though the diode is connected
to the 2.5V line, a power supply line is AC ground, thus C
D
is
connected to ground.
Figure 17
shows the schematic needed to derive F, the feed-
back factor, for a transimpedance amplifier. In this figure C
D
+ C
= C
. Therefore it is critical that the designer knows
the diode capacitance and the op amp input capacitance. The
photo diode is close to an ideal current source once its ca-
pacitance is included in the model. What kind of circuit is this
Without C
there is only an input capacitor and a feedback
resistor. This circuit is a differentiator! Remember, differen-
tiator circuits are inherently unstable and must be compen-
sated. In this case C
F
compensates the circuit.
20216364
FIGURE 17. Transimpedance Feedback Model
17
www.national.com
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LMV794MA/NOPB | 功能描述:運算放大器 - 運放 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 |
| LMV794MAX | 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 |
| LMV794MAX/NOPB | 功能描述:運算放大器 - 運放 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 |
| 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:運算放大器 - 運放 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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