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| 型號(hào)： | LMP2014MT |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運(yùn)算放大器 |
| 英文描述： | High Precision, Rail-to-Rail Output Operational Amplifier |
| 中文描述： | QUAD OP-AMP, 60 uV OFFSET-MAX, 3 MHz BAND WIDTH, PDSO14 |
| 封裝： | TSSOP-14 |
| 文件頁(yè)數(shù)： | 10/16頁(yè) |
| 文件大?。?/td> | 688K |
| 代理商： | LMP2014MT |
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Application Information
THE BENEFITS OF LMP201X
NO 1/f NOISE
Using patented methods, the LMP201X eliminates the 1/f
noise present in other amplifiers. That noise, which in-
creases as frequency decreases, is a major source of mea-
surement error in all DC-coupled measurements. Low-
frequency noise appears as a constantly-changing signal in
series with any measurement being made. As a result, even
when the measurement is made rapidly, this constantly-
changing noise signal will corrupt the result. The value of this
noise signal can be surprisingly large. For example: If a
conventional amplifier has a flat-band noise level of 10nV/
and a noise corner of 10 Hz, the RMS noise at 0.001
Hz is 1μV/
. This is equivalent to a 0.50 μV peak-to-
peak error, in the frequency range 0.001 Hz to 1.0 Hz. In a
circuit with a gain of 1000, this produces a 0.50 mV peak-
to-peak output error. This number of 0.001 Hz might appear
unreasonably low, but when a data acquisition system is
operating for 17 minutes, it has been on long enough to
include this error. In this same time, the LMP201X will only
have a 0.21 mV output error. This is smaller by 2.4 x. Keep
in mind that this 1/f error gets even larger at lower frequen-
cies. At the extreme, many people try to reduce this error by
integrating or taking several samples of the same signal.
This is also doomed to failure because the 1/f nature of this
noise means that taking longer samples just moves the
measurement into lower frequencies where the noise level is
even higher.
The LMP201X eliminates this source of error. The noise
level is constant with frequency so that reducing the band-
width reduces the errors caused by noise.
Another source of error that is rarely mentioned is the error
voltage caused by the inadvertent thermocouples created
when the common "Kovar type" IC package lead materials
are soldered to a copper printed circuit board. These steel-
based leadframe materials can produce over 35 μV/C when
soldered onto a copper trace. This can result in thermo-
couple noise that is equal to the LMP201X noise when there
is a temperature difference of only 0.0014C between the
lead and the board!
For this reason, the lead-frame of the LMP201X is made of
copper. This results in equal and opposite junctions which
cancel this effect. The extremely small size of the SOT-23
package results in the leads being very close together. This
further reduces the probability of temperature differences
and hence decreases thermal noise.
OVERLOAD RECOVERY
The LMP201X recovers from input overload much faster
than most chopper-stabilized op amps. Recovery from driv-
ing the amplifier to 2X the full scale output, only requires
about 40 ms. Many chopper-stabilized amplifiers will take
from 250 ms to several seconds to recover from this same
overload. This is because large capacitors are used to store
the unadjusted offset voltage.
The wide bandwidth of the LMP201X enhances performance
when it is used as an amplifier to drive loads that inject
transients back into the output.ADCs (Analog-to-Digital Con-
verters) and multiplexers are examples of this type of load.
To simulate this type of load, a pulse generator producing a
1V peak square wave was connected to the output through a
10 pF capacitor. (
Figure 1
) The typical time for the output to
recover to 1% of the applied pulse is 80 ns. To recover to
0.1% requires 860ns. This rapid recovery is due to the wide
bandwidth of the output stage and large total GBW.
NO EXTERNAL CAPACITORS REQUIRED
The LMP201X does not need external capacitors. This elimi-
nates the problems caused by capacitor leakage and dielec-
tric absorption, which can cause delays of several seconds
from turn-on until the amplifier’s error has settled.
MORE BENEFITS
The LMP201X offers the benefits mentioned above and
more. It has a rail-to-rail output and consumes only 950 μAof
supply current while providing excellent DC andAC electrical
performance. In DC performance, the LMP201X achieves
130 dB of CMRR, 120 dB of PSRR and 130 dB of open loop
gain. In AC performance, the LMP201X provides 3 MHz of
gain-bandwidth product and 4 V/μs of slew rate.
HOW THE LMP201X WORKS
The LMP201X uses new, patented techniques to achieve the
high DC accuracy traditionally associated with chopper-
stabilized amplifiers without the major drawbacks produced
by chopping. The LMP201X continuously monitors the input
offset and corrects this error. The conventional chopping
process produces many mixing products, both sums and
differences, between the chopping frequency and the incom-
ing signal frequency. This mixing causes large amounts of
distortion, particularly when the signal frequency approaches
the chopping frequency. Even without an incoming signal,
the chopper harmonics mix with each other to produce even
more trash. If this sounds unlikely or difficult to understand,
look at the plot (
Figure 2
), of the output of a typical (MAX432)
chopper-stabilized op amp. This is the output when there is
no incoming signal, just the amplifier in a gain of -10 with the
input grounded. The chopper is operating at about 150 Hz;
the rest is mixing products.Add an input signal and the noise
gets much worse. Compare this plot with
Figure 3
of the
LMP201X. This data was taken under the exact same con-
ditions. The auto-zero action is visible at about 30 kHz but
note the absence of mixing products at other frequencies.As
a result, the LMP201X has very low distortion of 0.02% and
very low mixing products.
20071516
FIGURE 1.
L
www.national.com
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMP2014MT/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 Quad,Hi Prec,Rro Op Amp 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 |
| LMP2014MT_05 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Quad High Precision, Rail-to-Rail Output Operational Amplifier |
| LMP2014MTX | 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 |
| LMP2014MTX/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 |
| LMP2014SD | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:High Precision, Rail-to-Rail Output Operational Amplifier |
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