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參數(shù)資料
| 型號(hào)： | LM4894 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 1 Watt Fully Differential Audio Power Amplifier With Shutdown Select |
| 中文描述： | 1瓦特全差分音頻功率放大器，具有關(guān)斷選擇 |
| 文件頁數(shù)： | 14/19頁 |
| 文件大小： | 770K |
| 代理商： | LM4894 |
Application Information
(Continued)
Tolerance R
F1
20%
10%
5%
1%
0%
R
F2
1.2R
1.1R
V
02
- V
01
-0.500V
-0.250V
I
LOAD
62.5mA
31.25mA
15.63mA
3.125mA
0
0.8R
0.9R
0.95R 1.05R -0.125V
0.99R 1.01R -0.025V
R
R
0
Similar results would occur if the input resistors were not
carefully matched. Adding input coupling capacitors in be-
tween the signal source and the input resistors will eliminate
this problem, however, to achieve best performance with
minimum component count it is highly recommended that
both the feedback and input resistors matched to 1% toler-
ance or better.
AUDIO POWER AMPLIFIER DESIGN
Design a 1W/8
Audio Amplifier
Given:
Power Output
Load Impedance
Input Level
Input Impedance
Bandwidth
1Wrms
8
1Vrms
20k
–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 Characteris-
tics
section.Asecond 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 mini-
mum supply voltage is (Vopeak +(V
+(V
)),
where V
and V
are extrapolated from the
Dropout Voltage vs Supply Voltage curve in the
Typical
Performance Characteristics
section.
(7)
Using the Output Power vs Supply Voltage graph for an 8W
load, the minimum supply rail just about 5V. Extra supply
voltage creates headroom that allows the LM4894 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 Dissipa-
tion
section. Once the power dissipation equations have
been addressed, the required differential gain can be deter-
mined from Equation 7.
(8)
R
f
/ R
i
= A
VD
From Equation 7, the minimum A
is 2.83. Since the de-
sired input impedance was 20k
, a ratio of 2.83:1 of R
to R
i
results in an allocation of R
= 20k
for both input resistors
and R
= 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, A
VD
.
With a A
VD
= 2.83 and f
H
= 100kHz, the resulting GBWP =
150kHz which is much smaller than the LM4894 GBWP of
10MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4894 can still be used without running into bandwidth
limitations.
L
www.national.com
14
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| LM4894IBP | 功能描述:IC AMP AUDIO PWR 1.4W MONO 9USMD RoHS:否 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) |
| LM4894ITL | 功能描述:IC AMP AUDIO PWR 1.4W MONO 9USMD RoHS:否 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) |
| LM4894ITLX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1 Watt Fully Differential Audio Power Amplifier With Shutdown Select |
| LM4894ITP/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) |
| LM4894LD | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1 Watt Fully Differential Audio Power Amplifier With Shutdown Select |
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