參數(shù)資料
型號: LM4871N/NOPB
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類: 音頻/視頻放大
英文描述: 1.5 W, 1 CHANNEL, AUDIO AMPLIFIER, PDIP8
封裝: DIP-8
文件頁數(shù): 3/16頁
文件大?。?/td> 472K
代理商: LM4871N/NOPB
Application Information (Continued)
lows the LM4871 to reproduce peaks in excess of 1W with-
out 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 differential gain can be determined from Equa-
tion 4.
(4)
R
f/Ri =AVD/2
(5)
From Equation 4, the minimum A
VD is 2.83; use AVD =3.
Since the desired input impedance was 20k
, and with a
A
VD impedance of 2, a ratio of 1.5:1 of Rf to Ri results in an
allocation of R
i = 20k
and R
f = 30k
. The final design step
is to address the bandwidth requirements which must be
stated as a pair of 3dB frequency points. Five times away
from a 3dB point is 0.17dB down from passband response
which is better than the required ±0.25dB specified.
f
L = 100Hz/5 = 20Hz
f
H = 20kHz*5= 100kHz
As stated in the External Components section, R
i in con-
junction with C
i create a highpass filter.
C
i
≥ 1/(2π*20k*20Hz) = 0.397F; use 0.39F
The high frequency pole is determined by the product of the
desired frequency pole, f
H, and the differential gain, AVD.
With a A
VD = 3 and fH = 100kHz, the resulting GBWP =
150kHz which is much smaller than the LM4871 GBWP of
4MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4871 can still be used without running into bandwidth
limitations.
Demonstration Board Layout
10000829
FIGURE 2. Recommended LD PC Board Layout:
Component-Side Silkscreen
10000830
FIGURE 3. Recommended LD PC Board Layout:
Component-Side Layout
10000831
FIGURE 4. Recommended LD PC Board Layout:
Bottom-Side Layout
LM4871
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相關代理商/技術參數(shù)
參數(shù)描述
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