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参数资料
| 型号： | LM4891MX/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 6/21页 |
| 文件大小： | 0K |
| 描述： | IC AMP AUDIO PWR 1W MONO 8SOIC |
| 标准包装： | 2,500 |
| 系列： | Boomer® |
| 类型： | AB 类 |
| 输出类型： | 1-通道（单声道） |
| 在某负载时最大输出功率 x 通道数量： | 1W x 1 @ 8 欧姆 |
| 电源电压： | 2.2 V ~ 5.5 V |
| 特点： | 消除爆音，关机，热保护 |
| 安装类型： | 表面贴装 |
| 供应商设备封装： | 8-SOIC |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 配用： | LM4891MBD-ND - BOARD EVALUATION LM4891M |
| 其它名称： | LM4891MX |
OBSOLETE
SNAS122E – MAY 2001 – REVISED APRIL 2013
AUDIO POWER AMPLIFIER DESIGN
A 1W/8
AUDIO AMPLIFIER
Given:
Power Output
1 Wrms
Load Impedance
8
Input Level
1 Vrms
Input Impedance
20 k
Bandwidth
100 Hz–20 kHz ± 0.25 dB
A designer must first determine the minimum supply rail to obtain the specified output power. By extrapolating
from the Output Power vs Supply Voltage graphs in the TYPICAL PERFORMANCE CHARACTERISTICS
section, the supply rail can be easily found. A second way to determine the minimum supply rail is to calculate
the required Vopeak using Equation 2 and add the output voltage. Using this method, the minimum supply voltage
would be (Vopeak + (VODTOP + VODBOT)), where VODBOT and VODTOP are extrapolated from the Dropout Voltage vs
Supply Voltage curve in the TYPICAL PERFORMANCE CHARACTERISTICS section.
(2)
5V is a standard voltage, in most applications, chosen for the supply rail. Extra supply voltage creates headroom
that allows the LM4891 to reproduce peaks in excess of 1W without 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 Equation 3.
(3)
AVD = (Rf/Ri) 2
Since the desired input impedance was 20 k
, and with a AVD of 3, a ratio of 1.5:1 of Rf to Ri results in an
allocation of Ri = 20 k and Rf = 30 k. The final design step is to address the bandwidth requirements which
must be stated as a pair of
3 dB frequency points. Five times away from a 3 dB point is 0.17 dB down from
passband response which is better than the required ±0.25 dB specified.
fL = 100 Hz/5 = 20 Hz
fH = 20 kHz * 5 = 100 kHz
As stated in the EXTERNAL COMPONENTS DESCRIPTION section, Ri in conjunction with Ci create a highpass
filter.
Ci ≥ 1/(2π*20 k*20 Hz) = 0.397 F; use 0.39 F
The high frequency pole is determined by the product of the desired frequency pole, fH, and the differential gain,
AVD. With a AVD = 3 and fH = 100 kHz, the resulting GBWP = 300 kHz which is much smaller than the LM4891
GBWP of 2.5 MHz. This figure displays that if a designer has a need to design an amplifier with a higher
differential gain, the LM4891 can still be used without running into bandwidth limitations.
14
Copyright 2001–2013, Texas Instruments Incorporated
Product Folder Links: LM4891
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4892 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1 Watt Audio Power Amplifier with Headphone Sense |
| LM48920B WAF | 制造商:Texas Instruments 功能描述: |
| LM4892B E WAF | 制造商:Texas Instruments 功能描述: |
| LM4892BUPN E WAF | 制造商:Texas Instruments 功能描述: |
| LM4892IBP | 功能描述:IC AMP AUDIO PWR 1W MONO 8USMD RoHS:否 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Boomer® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:DirectDrive® 类型:H 类 输出类型:耳机，2-通道（立体声） 在某负载时最大输出功率 x 通道数量:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
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