lm4919 National Semiconductor Corporation, lm4919 Datasheet - Page 14

• Manufacturer Part Number: lm4919
• Description: 1.5v, Mono 85mw Btl Output, 14mw Stereo Headphone Audio Amplifier
• Manufacturer: National Semiconductor Corporation

www.national.com
Application Information
for the supply rail. Extra supply voltage creates headroom
that allows the LM4919 to reproduce peak in excess of
10mW without producing audible distortion. At this time, the
designer must make sure that the power supply choice along
with the output impedance does not violate the conditions
explained in the Power Dissipation section. Once the power
dissipation equations have been addressed, the required
gain can be determined from Equation 2.
From Equation 4, the minimum AV is 1; use A
desired input impedance is 20k, and with a A
ratio of 1:1 results from Equation 1 for R
are chosen with R
is to address the bandwidth requirements which must be
stated as a pair of -3dB frequency points. Five times away
i
= 20k and R
f
= 20k. The final design step
f
(Continued)
to R. The values
V
V
= 1. Since the
gain of 1, a
(4)
14
from a -3dB point is 0.17dB down from passband response
which is better than the required
As stated in the External Components section, R
junction with C
The high frequency pole is determined by the product of the
desired frequency pole, fH, and the differential gain, A
an AV
which is much smaller than the LM4919 GBWP of 3MHz.
This example displays that if a designer has a need to design
an amplifier with higher differential gain, the LM4919 can still
be used without running into bandwidth limitations.
f
f
C
L
H
i
= 100Hz/5 = 20Hz
= 20kHz * 5 = 100kHz
≥ 1 / (2π * 20kΩ * 20Hz) = 0.397µF; use 0.39µF.
V
= 1 and f
i
creates a
H
= 100kHz, the resulting GBWP = 100kHz
±
0.25dB specified.
i
in con-
V
. With