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參數資料
| 型號： | LMH6624MFX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運算放大器 |
| 英文描述： | Single/Dual Ultra Low Noise Wideband Operational Amplifier |
| 中文描述： | OP-AMP, 750 uV OFFSET-MAX, PDSO5 |
| 封裝： | SOT-23, 5 PIN |
| 文件頁數： | 14/20頁 |
| 文件大小： | 985K |
| 代理商： | LMH6624MFX |
Application Section
INTRODUCTION
The LMH6624/LMH6626 are very wide gain bandwidth, ultra
low noise voltage feedback operational amplifiers. Their ex-
cellent performances enable applications such as medical
diagnostic ultrasound, magnetic tape & disk storage and
fiber-optics to achieve maximum high frequency signal-to-
noise ratios. The set of characteristic plots in the "Typical
Performance" section illustrates many of the performance
trade offs. The following discussion will enable the proper
selection of external components to achieve optimum sys-
tem performance.
BIAS CURRENT CANCELLATION
To cancel the bias current errors of the non-inverting con-
figuration, the parallel combination of the gain setting (R
g
)
and feedback (R
f
) resistors should equal the equivalent
source resistance (R
seq
) as defined in
Figure 1
. Combining
this constraint with the non-inverting gain equation also seen
in
Figure 1
, allows both R
f
and R
g
to be determined explicitly
from the following equations:
R
f
= A
V
R
seq
and R
g
= R
f
/(A
V
-1)
When driven from a 0
source, such as the output of an op
amp, the non-inverting input of the LMH6624/LMH6626
should be isolated with at least a 25
series resistor.
As seen in
Figure 2
, bias current cancellation is accom-
plished for the inverting configuration by placing a resistor
(R
) on the non-inverting input equal in value to the resis-
tance seen by the inverting input (R
||(R
+R
)). R
should to
be no less than 25
for optimum LMH6624/LMH6626 per-
formance. A shunt capacitor can minimize the additional
noise of R
b
.
TOTAL INPUT NOISE vs. SOURCE RESISTANCE
To determine maximum signal-to-noise ratios from the
LMH6624/LMH6626, an understanding of the interaction be-
tween the amplifier’s intrinsic noise sources and the noise
arising from its external resistors is necessary.
Figure 3
describes the noise model for the non-inverting
amplifier configuration showing all noise sources. In addition
to the intrinsic input voltage noise (e
) and current noise
(i
n
= i
n+
= i
n
) source, there is also thermal voltage noise
(e
=
√
(4KTR)) associated with each of the external resistors.
Equation 1 provides the general form for total equivalent
input voltage noise density (e
ni
). Equation 2 is a simplifica-
tion of Equation 1 that assumes
20058918
FIGURE 1. Non-Inverting Amplifier Configuration
20058919
FIGURE 2. Inverting Amplifier Configuration
20058920
FIGURE 3. Non-Inverting Amplifier Noise Model
L
www.national.com
14
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LMH6624MFX/HAPB | 制造商:Texas Instruments 功能描述: |
| LMH6624MFX/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 |
| LMH6624WG-QML | 制造商:Texas Instruments 功能描述:OP Amp Single Volt Fdbk ±6V/12V 10-Pin CPAK Tray |
| LMH6624WG-QMLV | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:ULTRA LOW NOISE WIDEBAND OP AMP |
| LMH6626 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Single/Dual Ultra Low Noise Wideband Operational Amplifier |
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