LM4900MMBD National Semiconductor, LM4900MMBD Datasheet - Page 15

• Manufacturer Part Number: LM4900MMBD
• Description: BOARD EVALUATION LM4900MM
• Manufacturer: National Semiconductor
• Series: Boomer®r

Specifications of LM4900MMBD

• Amplifier Type: Class AB
• Output Type: 1-Channel (Mono)
• Max Output Power X Channels @ Load: 675mW x 1 @ 8 Ohm
• Voltage - Supply: 2 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Board Type: Fully Populated
• Utilized Ic / Part: LM4900
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Information
From Equation 5, the minimum A
Since the desired input impedance was 20 kΩ, and with a
A
R
bandwidth requirements which must be stated as a pair of
−3 dB frequency points. Five times away from a pole gives
0.17 dB down from passband response which is better than
the required
As stated in the External Components section, R
junction with C
VD
i
= R
of 2, a ratio of 1:1 of R
F
= 20 kΩ. The final design step is to address the
±
0.25 dB specified.
i
create a highpass filter.
f
H
f
= 20kHz x 5 = 100kHz
L
= 100Hz/5 = 20Hz
F
to R
FIGURE 2. Differential Amplifier Configuration for LM4900
VD
i
results in an allocation of
is 1.55; use A
(Continued)
VD
i
in con-
= 2.
15
The high frequency pole is determined by the product of the
desired high frequency pole, f
A
100kHz which is much smaller than the LM4900 GBWP of
25MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4900 can still be used without running into bandwidth
problems.
VD
. With a A
C
i
≥ 1/(2π*20 kΩ*20 Hz) = 0.397µF; use 0.39µF
VD
= 2 and f
H
= 100kHz, the resulting GBWP =
H
, and the differential gain,
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