LM4940 datasheet(4/14 Pages) NSC

4 / 14 page

Typical Application

External Components Description Refer to (Figure 1.)

Components

Functional Description

This is the inverting input resistance that, along with R

F, sets the closed-loop gain. Input

resistance R

IN and input capacitance CIN form a high pass filter. The filter’s cutoff frequency is fC

=1/(2

πR

INCIN).

This is the input coupling capacitor. It blocks DC voltage at the amplifier’s inverting input. C

IN and

IN create a highpass filter. The filter’s cutoff frequency is fC =1/(2

πR

INCIN). Refer to the

SELECTING EXTERNAL COMPONENTS section for an explanation of determining C

IN’s value.

This is the feedback resistance that, along with R

i, sets closed-loop gain.

The supply bypass capacitor. Refer to the POWER SUPPLY BYPASSING section for information

about properly placing, and selecting the value of, this capacitor.

BYPASS

This capacitor filters the half-supply voltage present on the BYPASS pin. Refer to the Application

section, SELECTING EXTERNAL COMPONENTS, for information about properly placing, and

selecting the value of, this capacitor.

OUT

This is the output coupling capacitor. It blocks the nominal V

DD/2 voltage present at the output

and prevents it from reaching the load. C

OUT and RL form a high pass filter whose cutoff

frequency is f

C =1/(2

πR

LCOUT). Refer to the SELECTING EXTERNAL COMPONENTS section

for an explanation of determining C

OUT’s value.

20075672

FIGURE 2. Typical Stereo Audio Amplifier Application Circuit

LM4940 Datasheet(PDF) 4 Page - National Semiconductor (TI)