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參數(shù)資料
| 型號(hào)： | LM4925SD |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類(lèi)： | 音頻／視頻放大 |
| 英文描述： | Single Audio Amplifier |
| 中文描述： | 0.04 W, 2 CHANNEL, AUDIO AMPLIFIER, DSO10 |
| 封裝： | LLP-10 |
| 文件頁(yè)數(shù)： | 12/15頁(yè) |
| 文件大?。?/td> | 1046K |
| 代理商： | LM4925SD |
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Application Information
(Continued)
filter that limits low frequency response. This value should be
chosen based on needed frequency response and turn-on
time.
SELECTION OF INPUT CAPACITOR SIZE
Amplifying the lowest audio frequencies requires a high
value input coupling capacitor, Ci. A high value capacitor can
be expensive and may compromise space efficiency in por-
table designs. In many cases, however, the headphones
used in portable systems have little ability to reproduce
signals below 60Hz.Applications using headphones with this
limited frequency response reap little improvement by using
a high value input capacitor. In addition to system cost and
size, turn on time is affected by the size of the input coupling
capacitor Ci. A larger input coupling capacitor requires more
charge to reach its quiescent DC voltage. This charge
comes from the output via the feedback. Thus, by minimizing
the capacitor size based on necessary low frequency re-
sponse, turn-on time can be minimized. A small value of Ci
(in the range of 0.1μF to 0.47μF), is recommended.
AUDIO POWER AMPLIFIER DESIGN
A 25mW/32
Audio Amplifier
Given:
Power Output
Load Impedance
Input Level
Input Impedance
10mWrms
16
0.4Vrms
20k
A designer must first choose a mode of operation (SE or
BTL) and determine the minimum supply rail to obtain the
specified output power. By extrapolating from the Output
Power vs. Supply Voltage graphs in the Typical Performance
Characteristics section, the supply rail can be easily found.
3.0V is a standard voltage in most applications, it is chosen
for the supply rail. Extra supply voltage creates headroom
that allows the LM4925to reproduce peak in excess of
10mW without producing audible distortion. At this time, the
designer must make sure that the power supply choice along
with the output impedance does not violate the conditions
explained in the Power Dissipation section. Once the power
dissipation equations have been addressed, the required
gain can be determined from Equation 2.
(4)
From Equation 4, the minimumAV is 1; useA
V
= 1. Since the
desired input impedance is 20k, and with a A
V
gain of 1, a
ratio of 1:1 results from Equation 1 for R
f
to R. The values
are chosen with R
= 20k and R
= 20k. The final design step
is to address the bandwidth requirements which must be
stated as a pair of -3dB frequency points. Five times away
from a -3dB point is 0.17dB down from passband response
which is better than the required
±
0.25dB specified.
f
L
= 100Hz/5 = 20Hz
f
H
= 20kHz * 5 = 100kHz
As stated in the
External Components
section, R
i
in con-
junction with C
i
creates a
C
i
≥
1 / (2
π
* 20k
* 20Hz) = 0.397μF; use 0.39μF.
The high frequency pole is determined by the product of the
desired frequency pole, fH, and the differential gain,A
V
. With
an AV
V
= 1 and f
H
= 100kHz, the resulting GBWP = 100kHz
which is much smaller than the LM4925GBWP of 3MHz.
This example displays that if a designer has a need to design
an amplifier with higher differential gain, the LM4925can still
be used without running into bandwidth limitations.
L
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4925SD/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(lèi)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 |
| LM4925SDBD | 功能描述:BOARD EVALUATION LM4925SD RoHS:否 類(lèi)別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- |
| LM4925SDX | 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(lèi)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 |
| LM4925SDX/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(lèi)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 |
| LM4926 | 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Ground-Referenced, Ultra Low Noise, Fixed Gain, 80mW Stereo Headphone Amplifier |
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