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參數(shù)資料
| 型號(hào)： | LM4700T |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類(lèi)： | 音頻／視頻放大 |
| 英文描述： | 30 W, 1 CHANNEL, AUDIO AMPLIFIER, PZFM11 |
| 封裝： | TO-220, 11 PIN |
| 文件頁(yè)數(shù)： | 10/19頁(yè) |
| 文件大?。?/td> | 997K |
| 代理商： | LM4700T |
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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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PDF描述 |
|---|---|
| LM4700TF/NOPB | 30 W, 1 CHANNEL, AUDIO AMPLIFIER, PZFM11 |
| LM4701MWC | 30 W, 1 CHANNEL, AUDIO AMPLIFIER, UUC |
| LM4730TA/NOPB | 14 W, 2 CHANNEL, AUDIO AMPLIFIER, PZFM15 |
| LM4731TA/NOPB | 25 W, 2 CHANNEL, AUDIO AMPLIFIER, PZFM15 |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)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 類(lèi)別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Overture™ 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:DirectDrive® 類(lèi)型:H 類(lèi) 輸出類(lèi)型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，音量控制 安裝類(lèi)型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4701 | 制造商:NSC 制造商全稱: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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