LM4701 Datasheet, PDF (14/15 Pages) National Semiconductor (TI) – LM4701 Overture™ Audio Power Amplifier Series 30W Audio Power Amplifier with Mute and Standby Modes

Application Information (Continued)
point is 0.17 dB down from passband response which is bet-
ter than the required ±0.25 dB specified. This fact results in
a low and high frequency pole of 4 Hz and 100 kHz respec-
tively. As stated in the External Components section, R_I in
conjunction with C_I create a high-pass filter.
C_I ≥ 1/(2π * 1 kΩ * 4 Hz) = 39.8 µF; use 39 µF.
The high frequency pole is determined by the product of the
desired high frequency pole, f_H, and the gain, A_V. With a A_V
= 21 and f_H = 100 kHz, the resulting GBWP of 2.1 MHz is
less than the minimum GBWP of 5 MHz for the LM4701. This
will ensure that the high frequency response of the amplifier
will be no worse than 0.17 dB down at 20 kHz which is well
within the bandwidth requirements of the design.
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