- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄30750 > LM3875MWC (NATIONAL SEMICONDUCTOR CORP) 56 W, 1 CHANNEL, AUDIO AMPLIFIER, UUC PDF資料下載
參數(shù)資料
| 型號(hào)： | LM3875MWC |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 56 W, 1 CHANNEL, AUDIO AMPLIFIER, UUC |
| 封裝： | WAFER |
| 文件頁(yè)數(shù)： | 4/21頁(yè) |
| 文件大小： | 582K |
| 代理商： | LM3875MWC |
第1頁(yè)第2頁(yè)第3頁(yè)當(dāng)前第4頁(yè)第5頁(yè)第6頁(yè)第7頁(yè)第8頁(yè)第9頁(yè)第10頁(yè)第11頁(yè)第12頁(yè)第13頁(yè)第14頁(yè)第15頁(yè)第16頁(yè)第17頁(yè)第18頁(yè)第19頁(yè)第20頁(yè)第21頁(yè)
Application Information (Continued)
to case thermal resistance,
θ
JC,TJmax = 150C, and the rec-
ommended Thermalloy Thermacote thermal compound re-
sistance,
θ
CS.
SIGNAL-TO-NOISE RATIO
In the measurement of the signal-to-noise ratio, misinterpre-
tations of the numbers actually measured are common. One
amplifier may sound much quieter than another, but due to
improper testing techniques, they appear equal in measure-
ments. This is often the case when comparing integrated cir-
cuit designs to discrete amplifier designs. Discrete transistor
amps often “run out of gain” at high frequencies and there-
fore have small bandwidths to noise as indicated below.
Integrated circuits have additional open loop gain allowing
additional feedback loop gain in order to lower harmonic dis-
tortion and improve frequency response. It is this additional
bandwidth that can lead to erroneous signal-to-noise mea-
surements if not considered during the measurement pro-
cess. In the typical example above, the difference in band-
width appears small on a log scale but the factor of 10 in
bandwidth, (200 kHz to 2 MHz) can result in a 10 dB theoreti-
cal difference in the signal-to-noise ratio (white noise is pro-
portional to the square root of the bandwidth in a system).
In comparing audio amplifiers it is necessary to measure the
magnitude of noise in the audible bandwidth by using a
“weighting” filter (Note 11). A “weighting” filter alters the fre-
quency response in order to compensate for the average hu-
man ear’s sensitivity to the frequency spectra. The weighting
filters at the same time provide the bandwidth limiting as dis-
cussed in the previous paragraph.
Note 11: CCIR/ARM:
A Practical Noise Measurement Method; by Ray
Dolby, David Robinson and Kenneth Gundry, AES Preprint No. 1353 (F-3).
In addition to noise filtering, differing meter types give differ-
ent noise readings. Meter responses include:
1.
RMS reading,
2.
average responding,
3.
peak reading, and
4.
quasi peak reading.
Although theoretical noise analysis is derived using true
RMS based calculations, most actual measurements are
taken with ARM (Average Responding Meter) test equip-
ment.
Typical signal-to-noise figures are listed for an A-weighted fil-
ter which is commonly used in the measurement of noise.
The shape of all weighting filters is similar, with the peak of
the curve usually occurring in the 3 kHz–7 kHz region as
shown below.
SUPPLY BYPASSING
The LM3875 has excellent power supply rejection and does
not require a regulated supply. However, to eliminate pos-
sible oscillations all op amps and power op amps should
have their supply leads bypassed with low-inductance ca-
pacitors having short leads and located close to the package
terminals. Inadequate power supply bypassing will manifest
itself by a low frequency oscillation known as “motorboating”
or by high frequency instabilities. These instabilities can be
eliminated through multiple bypassing utilizing a large tanta-
lum or electrolytic capacitor (10 F or larger) which is used to
absorb low frequency variations and a small ceramic capaci-
tor (0.1 F) to prevent any high frequency feedback through
the power supply lines.
If adequate bypassing is not provided the current in the sup-
ply leads which is a rectified component of the load current
may be fed back into internal circuitry. This signal causes low
distortion at high frequencies requiring that the supplies be
bypassed at the package terminals with an electrolytic ca-
pacitor of 470 F or more.
LEAD INDUCTANCE
Power op amps are sensitive to inductance in the output
lead, particularly with heavy capacitive loading. Feedback to
the input should be taken directly from the output terminal,
minimizing common inductance with the load.
Lead inductance can also cause voltage surges on the sup-
plies. With long leads to the power supply, energy is stored in
the lead inductance when the output is shorted. This energy
can be dumped back into the supply bypass capacitors when
the short is removed. The magnitude of this transient is re-
duced by increasing the size of the bypass capacitor near
the IC. With at least a 20 F local bypass, these voltage
surges are important only if the lead length exceeds a couple
feet (>1 H lead inductance). Twisting together the supply
and ground leads minimizes the effect.
LAYOUT, GROUND LOOPS AND STABILITY
The LM3875 is designed to be stable when operated at a
closed-loop gain of 10 or greater, but as with any other
high-current amplifier, the LM3875 can be made to oscillate
under certain conditions. These usually involve printed cir-
cuit board layout or output/input coupling.
When designing a layout, it is important to return the load
ground, the output compensation ground, and the low level
(feedback and input) grounds to the circuit board common
ground point through separate paths. Otherwise, large cur-
rents flowing along a ground conductor will generate volt-
ages on the conductor which can effectively act as signals at
the input, resulting in high frequency oscillation or excessive
distortion. It is advisable to keep the output compensation
components and the 0.1 F supply decoupling capacitors as
close as possible to the LM3875 to reduce the effects of PCB
DS011449-11
DS011449-12
LM3875
www.national.com
12
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM3875MDC | 56 W, 1 CHANNEL, AUDIO AMPLIFIER, UUC |
| LM3876CCT | 40 W, 1 CHANNEL, AUDIO AMPLIFIER, PSFM11 |
| LM3876DWF | 56 W, 1 CHANNEL, AUDIO AMPLIFIER, UUC |
| LM3876MWC | 56 W, 1 CHANNEL, AUDIO AMPLIFIER, UUC |
| LM3876MDC | 56 W, 1 CHANNEL, AUDIO AMPLIFIER, UUC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3875T | 功能描述:IC AMP AUDIO PWR 56W AB TO220-11 RoHS:是 類別: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® 類型:H 類 輸出類型: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) |
| LM3875T | 制造商:Texas Instruments 功能描述:IC AMP AUDIO 100W 3875 SIL-11 |
| LM3875T/NOPB | 制造商:Texas Instruments 功能描述:Audio Amp Speaker 1-CH Mono 56W Class-AB 11-Pin(11+Tab) TO-220 |
| LM3875TF | 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 |
| LM3875TF/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 |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。