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参数资料
| 型号： | LM4700T |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 30 W, 1 CHANNEL, AUDIO AMPLIFIER, PZFM11 |
| 封装： | TO-220, 11 PIN |
| 文件页数： | 10/19页 |
| 文件大小： | 997K |
| 代理商： | LM4700T |
Application Information (Continued)
may reduce pops resulting from power supplies that ramp
extremely quick or exhibit overshoot during system turn-on.
AUDIO POWER AMPLlFIER DESIGN
Design a 25W/8
Audio Amplifier
Given:
Power Output
25 Wrms
Load Impedance
8
Input Level
1 Vrms(max)
Input Impedance
47 k
Bandwidth
20 Hz to 20 kHz ± 0.25 dB
A designer must first determine the power supply require-
ments in terms of both voltage and current needed to obtain
the specified output power. V
OPEAK can be determined from
equation (4) and I
OPEAK from equation (5).
(4)
(5)
To determine the maximum supply voltage, the following
conditions must be considered. Add the dropout voltage to
the peak output swing V
OPEAK, to get the supply rail at a
current of I
OPEAK. The regulation of the supply determines
the unloaded voltage which is usually about 15% higher. The
supply voltage will also rise 10% during high line conditions.
Therefore the maximum supply voltage is obtained from the
following equation:
Max Supplies
≈ ± (V
OPEAK +VOD) (1 + Regulation) (1.1)
For 25W of output power into an 8
load, the required
V
OPEAK is 20V. A minimum supply rail of ±25V results from
adding V
OPEAK and VOD. With regulation, the maximum
supplies are ±31.7V and the required I
OPEAK is 2.5A from
equation (5). At this point it is a good idea to check the Power
Output vs Supply Voltage to ensure that the required output
power is obtainable from the device while maintaining low
THD+N. In addition, the designer should verify that with the
required power supply voltage and load impedance, that the
required heatsink value
θ
SA is feasible given system cost
and size constraints. Once the heatsink issues have been
addressed, the required gain can be determined from equa-
tion (6).
(6)
From equation (6), the minimum A
V is AV
≥ 14.14.
By selecting a gain of 21, and with a feedback resistor, R
F =
20 k
, the value of R
I follows from equation (7).
R
I =RF (AV 1)
(7)
Thus with R
J =1k
a non-inverting gain of 21 will result.
Since the desired input impedance was 47 k
, a value of
47 k
was selected for R
IN. 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. This fact
results in a low and high frequency pole of 4 Hz and 100 kHz
respectively. As stated in the External Components sec-
tion, R
I in conjunction with CI create a high-pass filter.
C
I
≥ 1/(2π *1k * 4 Hz) = 39.8 F; use 39 F.
The high frequency pole is determined by the product of the
desired high frequency pole, f
H, and the gain, AV. With a AV
= 21 and f
H = 100 kHz, the resulting GBWP of 2.1 MHz is
less than the minimum GBWP of 5 MHz for the LM4700. This
will ensure that the high frequency response of the amplifier
will be no worse than 0.17 dB down at 20 kHz which is well
within the bandwidth requirements of the design.
LM4700
www.national.com
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM4700T/NOPB | 制造商:Texas Instruments 功能描述: |
| LM4700TF | 制造商:Texas Instruments 功能描述:IC AMP + MUTE 30W 4700 TO-220-11 |
| LM4700TF | 制造商:Texas Instruments 功能描述:IC AMP + MUTE 30W 4700 TO-220-11 |
| LM4700TF/NOPB | 功能描述:IC AMP AUDIO PWR 30W AB TO220-11 RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:Overture™ 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) |
| LM4701 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:LM4701 Overture⑩ Audio Power Amplifier Series 30W Audio Power Amplifier with Mute and Standby Modes |
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