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参数资料
| 型号： | LM4892M/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, PDSO8 |
| 封装： | SOIC-8 |
| 文件页数： | 4/22页 |
| 文件大小： | 1037K |
| 代理商： | LM4892M/NOPB |
Application Information (Continued)
create pops upon device enable. Thus, by minimizing the
capacitor size based on necessary low frequency response,
turn-on pops can be minimized.
Besides minimizing the input capacitor size, careful consid-
eration should be paid to the bypass capacitor value. Bypass
capacitor, C
B, is the most critical component to minimize
turn-on pops since it determines how fast the LM4892 turns
on. The slower the LM4892’s outputs ramp to their quiescent
DC voltage (nominally 1/2 V
DD), the smaller the turn-on pop.
Choosing C
B equal to 1.0F along with a small value of Ci (in
the range of 0.1F to 0.39F), should produce a virtually
clickless and popless shutdown function. While the device
will function properly, (no oscillations or motorboating), with
C
B equal to 0.1F, the device will be much more susceptible
to turn-on clicks and pops. Thus, a value of C
B equal to
1.0F is recommended in all but the most cost sensitive
designs.
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 Per-
formance Characteristics section, the supply rail can be
easily found. A second way to determine the minimum sup-
ply rail is to calculate the required V
opeak using Equation 2
and add the output voltage. Using this method, the minimum
supply voltage would be (V
opeak +(VODTOP +VODBOT)), where
V
ODBOT and VODTOP are extrapolated from the Dropout Volt-
age vs Supply Voltage curve in the Typical Performance
Characteristics section.
(2)
5V is a standard voltage in most applications, it is chosen for
the supply rail. Extra supply voltage creates headroom that
allows the LM4892 to reproduce peaks in excess of 1W
without producing audible distortion. At this time, the de-
signer 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 3.
(3)
R
f/Ri =AVD/2
From Equation 3, the minimum A
VD is 2.83; use AVD =3.
Since the desired input impedance was 20k
, and with a
A
VD of 3, 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*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, 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 LM4892 GBWP of
4 MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4892 can still be used without running into bandwidth
limitations.
LM4892
www.national.com
12
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相关代理商/技术参数 |
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| LM4892MX/NOPB | 功能描述:IC AMP AUDIO PWR 1W MONO 8SOIC RoHS:是 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) |
| LM4893 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:1.1 Watt Audio Power Amplifier |
| LM4893ITL | 制造商:Texas Instruments 功能描述:AMP POWER AUDIO 1.1W SMD BUMP-9 |
| LM4893ITL/NOPB | 功能描述:IC AMP AUDIO PWR 1.1W MONO 9USMD RoHS:是 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) |
| LM4893ITLBD | 功能描述:BOARD EVALUATION LM4893ITL 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:- |
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