Vsup+

+

RF

RI

Vsup-

LM224K, LM224KA, LM324, LM324A, LM324K, LM324KA, LM2902

LM124, LM124A, LM224, LM224A, LM2902V, LM2902K, LM2902KV, LM2902KAV

SLOS066W – SEPTEMBER 1975 – REVISED MARCH 2015

www.ti.com

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. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The LMx24 and LM2902 operational amplifiers are useful in a wide range of signal conditioning applications.

Inputs can be powered before VCC for flexibility in multiple supply circuits.

9.2 Typical Application

A typical application for an operational amplifier in 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.

Figure 9. Application Schematic

9.2.1 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 will scale a signal of ±0.5 V to ±1.8 V. Setting the supply at ±12 V is sufficient to

accommodate this application.

9.2.2 Detailed Design Procedure

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

(1)

(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 will use currents in the milliamp range. This ensures the part will not draw

too much current. This example will choose 10 k

Ω for RI which means 36 kΩ will be used for RF. This was

determined by Equation 3.

(3)

12

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