LM4910
SNAS151G – MAY 2004 – REVISED MARCH 2007
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HIGHER GAIN AUDIO AMPLIFIER
The LM4910 is unity-gain stable and requires no external components besides gain-setting resistors, input
coupling capacitors, and proper supply bypassing in the typical application. However, if a very large closed-loop
differential gain is required, a feedback capacitor (C
f
) may be needed as shown in
Figure 11
to bandwidth limit
the amplifier. This feedback capacitor creates a low pass filter that eliminates possible high frequency
oscillations. Care should be taken when calculating the -3dB frequency in that an incorrect combination of R
f
and
C
f
will cause frequency response roll off before 20kHz. A typical combination of feedback resistor and capacitor
that will not produce audio band high frequency roll off is Rf = 20k
Ω
and C
f
= 25pF. These components result in
a -3dB point of approximately 320kHz.
REFERENCE DESIGN BOARD and LAYOUT GUIDELINES MSOP & SO BOARDS
(Note: R
PU
2 is not required. It is used for test measurement purposes only.)
16
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