 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LMP2014MTX Datasheet(PDF) 10 Page - National Semiconductor (TI) |
|
|
||||||||||||||||||||||||||||||
LMP2014MTX Datasheet(HTML) 10 Page - National Semiconductor (TI) |
|
|
10 / 16 page  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 0.0014˚C 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 µA of supply current while providing excellent DC and AC 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. www.national.com 10 |
Similar Part No. - LMP2014MTX |
|
Similar Description - LMP2014MTX |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
