LMP7702MASLASHNOPB datasheet(21/44 Pages) TI1

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LMP7701, LMP7702, LMP7704

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SNOSAI9I – SEPTEMBER 2005 – REVISED NOVEMBER 2015

8 Detailed Description

8.1 Overview

The LMP770x are single, dual, and quad low offset voltage, rail-to-rail input and output precision amplifiers each

with a CMOS input stage and wide supply voltage range of 2.7V to 12V. The LMP770x have a very low input

bias current of only ±200 fA at room temperature.

The wide supply voltage range of 2.7V to 12V over the extensive temperature range of

−40°C to 125°C makes

the LMP770x excellent choices for low voltage precision applications with extensive temperature requirements.

The LMP770x have only ±37

μV of typical input referred offset voltage and this offset is specified to be less than

±500

μV for the single and ±520 μV for the dual and quad, over temperature. This minimal offset voltage allows

more accurate signal detection and amplification in precision applications.

The low input bias current of only ±200 fA along with the low input referred voltage noise of 9 nV/

√Hz gives the

LMP770x superiority for use in sensor applications. Lower levels of noise from the LMP770x mean of better

signal fidelity and a higher signal-to-noise ratio.

Texas Instruments is heavily committed to precision amplifiers and the market segment they serve. Technical

support and extensive characterization data is available for sensitive applications or applications with a

constrained error budget.

The LMP7701 is offered in the space saving 5-Pin SOT-23 and 8-Pin SOIC package. The LMP7702 comes in

the 8-Pin SOIC and 8-Pin VSSOP package. The LMP7704 is offered in the 14-Pin SOIC and 14-Pin TSSOP

package. These small packages are ideal solutions for area constrained PC boards and portable electronics.

8.2 Functional Block Diagram

Figure 40. Functional Block Diagram (LMP7701)

8.3 Feature Description

8.3.1 Capacitive Load

The LMP770x can each be connected as a non-inverting unity gain follower. This configuration is the most

sensitive to capacitive loading.

The combination of a capacitive load placed on the output of an amplifier along with the amplifier's output

impedance creates a phase lag which in turn reduces the phase margin of the amplifier. If the phase margin is

significantly reduced, the response will be either underdamped or it will oscillate.

To drive heavier capacitive loads, an isolation resistor, RISO, in Figure 41 should be used. By using this isolation

resistor, the capacitive load is isolated from the amplifier's output, and hence, the pole caused by CL is no longer

in the feedback loop. The larger the value of RISO, the more stable the output voltage will be. If values of RISO are

sufficiently large, the feedback loop will be stable, independent of the value of CL. However, larger values of RISO

result in reduced output swing and reduced output current drive.

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Product Folder Links: LMP7701 LMP7702 LMP7704

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