Power Supply

Rejection Ratio

Open Loop

Frequency Response

20026721

20026722

Supply Current vs

Supply Voltage

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External Components Description

( Refer to Figure 1. )

Components

Functional Description

1.

R

i

This is the inverting input resistance that sets the closed-loop gain in conjunction with R

forms a high pass filter with C

πR

2.

C

i

This is the input coupling capacitor. It blocks the DC voltage at the amplifier’s input terminals. It also

creates a highpass filter with R

πR

for an explanation of how to determine the value of C

3.

R

f

This is the feedback resistance. It sets the closed-loop gain in conjunction with R

4.

C

s

This is the supply bypass capacitor. It provides power supply filtering. Refer to the Power Supply

Bypassing section for information concerning proper placement and selection of the supply bypass

capacitor.

5.

C

B

This is the bypass pin capacitor. It provides half-supply filtering. Refer to the section, Proper Selection of

External Components, for information concerning proper placement and selection of C

Application Information

ELIMINATING OUTPUT COUPLING CAPACITORS

Typical single-supply audio amplifiers that can switch be-

tween

driving

bridge-tied-load

(BTL)

speakers

and

single-ended (SE) headphones use a coupling capacitor on

each SE output. This capacitor blocks the half-supply volt-

age to which the output amplifiers are typically biased and

couples the audio signal to the headphones. The signal

return to circuit ground is through the headphone jack’s

sleeve.

The LM4868 eliminates these coupling capacitors. Amp2A is

internally configured to apply V

jack’s sleeve. This voltage matches the quiescent voltage

present on the Amp1A and Amp1B outputs that drive the

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