LMP2021/

LMP2022

RIN/RF

IN

+

-

RIN

RF

RFILT

LMV771

-

+

RFILT

OUT

CFILT

IN

+

-

RIN//RF

RF

RIN

CF

17

LMP2021, LMP2022

www.ti.com

SNOSAY9G – SEPTEMBER 2008 – REVISED FEBRUARY 2016

Product Folder Links: LMP2021 LMP2022

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Copyright © 2008–2016, Texas Instruments Incorporated

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

8.1.1 Achieving Lower Noise With Filtering

The low input voltage noise of the LMP202x, and no 1/f noise make these suitable for many applications with

noise sensitive designs. Simple filtering can be done on the LMP202x to remove high frequency noise. Figure 37

shows a simple circuit that achieves this.

In Figure 37 CF and the corner frequency of the filter resulting from CF and RF will reduce the total noise.

Figure 37. Noise Reducing Filter for Lower Gains

In order to achieve lower noise floors for even more noise stringent applications, a simple filter can be added to

the op amp’s output after the amplification stage. Figure 38 shows the schematic of a simple circuit which

achieves this objective. Low noise amplifiers such as the LMV771 can be used to create a single pole low pass

filter on the output of the LMP202x. The noise performance of the filtering amplifier, LMV771 in this circuit, will

not be dominant as the input signal on LMP202x has already been significantly gained up and as a result the

effect of the input voltage noise of the LMV771 is effectively not noticeable.

Figure 38. Enhanced Filter to Further Reduce Noise at Higher Gains