LM4924 datasheet(12/16 Pages) NSC

Part #	LM4924

Description	2 Cell Battery, 40mW Per Channel Output Capacitor-Less(OCL) Stereo Headphone Audio Amplifier

PDF	16 Pages

Scroll/Zoom	100%

Manufacturer	NSC [National Semiconductor (TI)]

Direct Link	http://www.national.com

Logo

12 / 16 page

Application Information (Continued)

As mentioned in the Selecting Proper External Compo-

nents section, R

i and Ci create a highpass filter that sets the

amplifier’s lower bandpass frequency limit. Find the coupling

capacitor’s value using Equation (3).

≥ 1/(2πR

ifL)

(5)

The result is

1/(2

π*20kΩ*20Hz) = 0.397µF

Use a 0.39µF capacitor, the closest standard value.

The high frequency pole is determined by the product of the

desired frequency pole, f

H, and the differential gain, AV. With

an A

V = 1 and fH = 100kHz, the resulting GBWP = 100kHz

which is much smaller than the LM4924 GBWP of 11MHz.

This figure displays that if a designer has a need to design

an amplifier with higher differential gain, the LM4924 can still

be used without running into bandwidth limitations.

HIGHER GAIN AUDIO AMPLIFIER

20121029

FIGURE 3.

LM4924 Datasheet(PDF) 12 Page - National Semiconductor (TI)