9 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, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

The LM2902-Q1, LM2902B-Q1, LM2902BA-Q1 operational amplifiers are useful in a wide range of signal

conditioning applications. Inputs can be powered before VS for flexibility in multiple supply circuits. For full

application design guidelines related to this family of devices, please refer to the application report Application

design guidelines for LM324/LM358 devices.

9.2 Typical Application

A typical application for an operational amplifier is an inverting amplifier. This amplifier takes a positive voltage

on the input, and makes it a negative voltage of the same magnitude. In the same manner, it also makes

negative voltages positive.

Vsup+

+

VOUT

RF

VIN

RI

Vsup-

Figure 9-1. Application Schematic

9.3 Design Requirements

The supply voltage must be chosen such that it is larger than the input voltage range and output range. For

instance, this application scales a signal of ±0.5 V to ±1.8 V. Setting the supply at ±12 V is sufficient to

accommodate this application.

9.4 Detailed Design Procedure

Determine the gain required by the inverting amplifier using Equation 1 and Equation 2:

V

VOUT

A

VIN

(1)

V

1.8

A

3.6

0.5

(2)

Once the desired gain is determined, choose a value for RI or RF. Choosing a value in the kilohm range is

desirable because the amplifier circuit uses currents in the milliampere range. This ensures the part does not

draw too much current. This example uses 10 kΩ for RI which means 36 kΩ is used for RF. This was determined

by Equation 3.

V

RF

A

RI

(3)

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LM2902-Q1, LM2902B-Q1, LM2902BA-Q1

SGLS178G – AUGUST 2003 – REVISED FEBRUARY 2023

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