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参数资料
| 型号： | LM4898ITLX/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PBGA9 |
| 封装： | MICRO SMD-9 |
| 文件页数： | 6/17页 |
| 文件大小： | 596K |
| 代理商： | LM4898ITLX/NOPB |
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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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4898LD | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| LM4898LD/NOPB | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| LM4898LDBD | 功能描述:BOARD EVALUATION LM4898LD RoHS:否 类别:编程器，开发系统 >> 评估板 - 音频放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- |
| LM4898LDX | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| LM4898LDX/NOPB | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
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