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參數(shù)資料
| 型號(hào)： | LM4818M/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 0.35 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8 |
| 封裝： | SOP-8 |
| 文件頁數(shù)： | 3/16頁 |
| 文件大?。?/td> | 483K |
| 代理商： | LM4818M/NOPB |
Application Information (Continued)
C
B
T
ON
0.01F
20ms
0.1F
200ms
0.22F
440ms
0.47F
940ms
1.0F
2S
In order to eliminate "clicks and pops", all capacitors must be
discharged before turn-on. Rapidly switching V
DD may not
allow the capacitors to fully discharge, which may cause
"clicks and pops".
AUDIO POWER AMPLIFIER DESIGN EXAMPLE
The following are the desired operational
parameters:
Given:
Power Output
100mW
Load Impedance
16
Input Level
1Vrms (max)
Input Impedance
20k
Bandwidth
100Hz–20kHz ± 0.25dB
The design begins by specifying the minimum supply voltage
necessary to obtain the specified output power. To find this
minimum supply voltage, use the Output Power vs. Supply
Voltage graph in the Typical Performance Characteristics
section. From the graph for a 16
load, (graphs are for 8,
16
, and 32 loads) the supply voltage for 100mW of output
power with 1% THD+N is approximately 3.15 volts.
Additional supply voltage creates the benefit of increased
headroom that allows the LM4818 to reproduce peaks in
excess of 100mW without output signal clipping or audible
distortion. The choice of supply voltage must also not create
a situation that violates maximum dissipation as explained
above in the Power Dissipation section. For example, if a
3.3V supply is chosen for extra headroom then according to
Equation (3) the maximum power dissipation point with a
16
load is 138mW. Using Equation (4) the maximum am-
bient temperature is 126C for the M08A package.
After satisfying the LM4818’s power dissipation require-
ments, the minimum differential gain is found using Equation
(6).
(6)
Thus a minimum gain of 1.27 V/V allows the LM4818 to
reach full output swing and maintain low noise and THD+N
performance. For this example, let A
VD = 1.27. The amplifi-
er’s overall gain is set using the input (R
i) and feedback (RF)
resistors. With the desired input impedance set to 20k
, the
feedback resistor is found using Equation (7).
R
F/Ri =AVD/2 (V/V)
(7)
The value of R
F is 13k
.
The last step in this design example is setting the amplifier’s
-3dB frequency bandwidth. To achieve the desired ±0.25dB
pass band magnitude variation limit, the low frequency re-
sponse must extend to at least one-fifth the lower bandwidth
limit and the high frequency response must extend to at least
five times the upper bandwidth limit. The gain variation for
both response limits is 0.17dB, well with in the ±0.25dB
desired limit.
The results are:
f
L = 100Hz/5 = 20Hz
f
H = 20 kHz*5 = 100kHz
As mentioned in the External Components section, R
i and
C
i create a high pass filter that sets the amplifier’s lower
band pass frequency limit. Find the coupling capacitor’s
value using Equation (8).
C
i
≥ 1/(2πR
ifc) (F)
(8)
C
i
≥ 0.398F, a standard value of 0.39F will be used. The
product of the desired high frequency cutoff (100kHz in this
example) and the differential gain, A
VD, determines the up-
per pass band response limit. With A
VD = 1.27 and fH =
100kHz, the closed-loop gain bandwidth product (GBWP) is
127kHz. This is less than the LM4818’s 900kHz GBWP. With
this margin the amplifier can be used in designs that require
more differential gain while avoiding performance restricting
bandwidth limitations.
LM4818
www.national.com
11
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4818MX | 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 |
| LM4818MX/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 |
| LM4819 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:350mW Audio Power Amplifier with Shutdown Mode |
| LM4819LD | 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 |
| LM4819LD/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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