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參數(shù)資料
| 型號(hào)： | LM4898MMXNPAU |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO10 |
| 封裝： | MSOP-10 |
| 文件頁數(shù)： | 6/17頁 |
| 文件大?。?/td> | 596K |
| 代理商： | LM4898MMXNPAU |
Application Information (Continued)
AUDIO POWER AMPLIFIER DESIGN
Design a 1W/8
Audio Amplifier
Given:
Power Output
1W
Load Impedance
8
Input Level
1Vrms
Input Impedance
20k
Bandwidth
100Hz–20kHz ± 0.25dB
A designer must first determine the minimum supply rail to
obtain the specified output power. The supply rail can easily
be found by extrapolating from the Output Power vs. Supply
Voltage graphs in the Typical Performance Characteristics
section. A second way to determine the minimum supply rail
is to calculate the required Vopeak using Equation 7 and add
the dropout voltages. Using this method, the minimum sup-
ply voltage is (Vopeak +(V
DO TOP+(VDO BOT )),where VDO
BOT
and V
DO TOP are extrapolated from the Dropout Voltage
vs. Supply Voltage curve in the Typical Performance Char-
acteristics section.
(7)
Using the Output Power vs. Supply Voltage graph for an 8
load, the minimum supply rail just about 5V. Extra supply
voltage creates headroom that allows the LM4898 to repro-
duce peaks in excess of 1W without producing audible dis-
tortion. 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 Equation 8.
(8)
R
f /Ri =AVD
From Equation 8, the minimum A
VD is 2.83. Since the de-
sired input impedance was 20k
, a ratio of 2.83:1 of R
f to Ri
results in an allocation of R
i = 20k
for both input resistors
and R
f= 60k
for both feedback resistors. The final design
step is to address the bandwidth requirement which must be
stated as a single -3dB frequency point. Five times away
from a -3dB point is 0.17dB down from passband response
which is better than the required ±0.25dB specified.
f
H = 20kHz * 5 =100kHz
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 = 2.83 and fH = 100kHz, the resulting GBWP =
150kHz which is much smaller than the LM4898 GBWP of
10MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4898 can still be used without running into bandwidth
limitations.
LM4898
www.national.com
14
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| LM4899ITL/NOPB | 功能描述:IC AMP AUDIO PWR 1.4W MONO 9USMD RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類型:H 類 輸出類型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，音量控制 安裝類型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
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