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參數(shù)資料
| 型號(hào)： | LM4876 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 1.1W Audio Power Amplifier with Shutdown Logic Low |
| 中文描述： | 1.1W音頻功率放大器，帶有關(guān)斷邏輯低 |
| 文件頁(yè)數(shù)： | 8/9頁(yè) |
| 文件大?。?/td> | 247K |
| 代理商： | LM4876 |
Application Information
(Continued)
AUDIO POWER AMPLIFIER DESIGN
Design a 1W/8
Audio Amplifier
Given:
Power Output
Load Impedance
Input Level
Input Impedance
Bandwidth
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
using Equation 3
and add the output voltage. Using this method, the minimum
supply voltage would be (V
+ (V
+ V
)), where
V
and V
are extrapolated from the Dropout Volt-
age vs Supply Voltage curve in the
Typical Performance
Characteristics
section.
1 Wrms
8
1 Vrms
20 k
100 Hz–20 kHz
±
0.25 dB
(3)
Using the Output Power vs Supply Voltage graph for an 8
load, the minimum supply rail is 4.6V. But since 5V is a stan-
dard voltage in most applications, it is chosen for the supply
rail. Extra supply voltage creates headroom that allows the
LM4876 to reproduce peaks in excess of 1W without produc-
ing audible distortion. At this time, the designer must make
sure that the power supply choice along with the output im-
pedance 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 4.
(4)
R
f
/R
i
= A
VD
/2
(5)
From Equation 4, the minimum A
VD
is 2.83; use A
VD
= 3.
Since the desired input impedance was 20 k
, and with a
A
impedance of 2, a ratio of 1.5:1 of R
to R
results in an
allocation of R
= 20 k
and R
= 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 kHz
As stated in the
External Components
section, R
i
in con-
junction with C
i
create a highpass filter.
C
i
≥
1/(2
π
*20 k
*20 Hz) = 0.397 μF; use 0.39 μF
The high frequency pole is determined by the product of the
desired frequency pole, f
, and the differential gain, A
.
With a A
= 3 and f
= 100 kHz, the resulting GBWP =
150 kHz which is much smaller than the LM4876 GBWP of
4 MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4876 can still be used without running into bandwidth limi-
tations.
L
www.national.com
8
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4876_03 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1.1W Audio Power Amplifier with Logic Low Shutdown |
| LM4876M | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4876M/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4876MM | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4876MM/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
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