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参数资料
| 型号： | LM4870MX |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 1.1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO16 |
| 封装： | SOIC-16 |
| 文件页数： | 9/11页 |
| 文件大小： | 283K |
| 代理商： | LM4870MX |
Application Information (Continued)
are required for 1.0W of output power. Since 5V rails are
common, it is chosen to be the supply voltage. Supply volt-
age (up to a maximum of 5.5V) above the required 4.6V will
allow the LM4870 to reproduce transient signals at greater
than 1.0W of output power. The extra voltage will also in-
crease the device power dissipation, so the designer must
make sure that the conditions explained in the Power Dissi-
pationsection are not violated.
Once the power dissipation issues have been addressed,
the required differential gain can be determined from Equa-
tion 4:
From equation 4, the minimum A
vd is A vd = 2.83; use Avd=
3.
Since the amplifier output is bridged, giving a gain of 2, and
the desired system gain is 3, the ratio of feedback (R
f)toin-
put (R
i) resistor is 1.5:1. If Ri is set to the required input im-
pedance of 20 k
, then R
f =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.
f
L = 100 Hz/5 = 20 Hz
f
H = 20 kHz∏5 = 100 HzAs stated in the External Com-
ponents section, R
i in conjunction with Ci create a high-
pass 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 high frequency pole, f
H, and the differential gain, A
vd
. With a A
vd = 3 and fH = 100 kHz, the resulting GBWP =
150 kHz which is much smaller than the LM4870 GBWP of
4 MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4870 can still be used without running into bandwidth
problems.
LM4870
www.national.com
7
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4871 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:3W Audio Power Amplifier with Shutdown Mode |
| LM4871_03 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:3W Audio Power Amplifier with Shutdown Mode |
| LM4871LD | 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 |
| LM4871LD/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 |
| LM4871LDX | 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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