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参数资料
| 型号： | LM1875TLB03/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 25 W, 1 CHANNEL, AUDIO AMPLIFIER, PZFM5 |
| 封装： | PLASTIC, TO-220, 5 PIN |
| 文件页数： | 9/11页 |
| 文件大小： | 482K |
| 代理商： | LM1875TLB03/NOPB |
Application Hints (Continued)
output stage and constant power dissipation in all other parts
of the circuit. The curves of “Power Dissipation vs Power
Output” give a better representation of the behavior of the
LM1875 with various power supply voltages and resistive
loads. As an example, if the LM1875 is operated on a 50V
power supply with a resistive load of 8
, it can develop up to
19W of internal power dissipation. If the die temperature is to
remain below 150C for ambient temperatures up to 70C,
the total junction-to-ambient thermal resistance must be less
than
Using
θ
JC=2C/W, the sum of the case-to-heat-sink interface
thermal resistance and the heat-sink-to-ambient thermal re-
sistance must be less than 2.2C/W. The case-to-heat-sink
thermal resistance of the TO-220 package varies with the
mounting method used. A metal-to-metal interface will be
about 1C/W if lubricated, and about 1.2C/W if dry.
If a mica insulator is used, the thermal resistance will be
about 1.6C/W lubricated and 3.4C/W dry. For this example,
we assume a lubricated mica insulator between the LM1875
and the heat sink. The heat sink thermal resistance must
then be less than
4.2C/W2C/W1.6C/W=0.6C/W.
This is a rather large heat sink and may not be practical in
some applications. If a smaller heat sink is required for
reasons of size or cost, there are two alternatives.
[EM00001]The maximum ambient operating temperature
can be reduced to 50C (122F), resulting in a 1.6C/W heat
sink, or the heat sink can be isolated from the chassis so the
mica washer is not needed. This will change the required
heat sink to a 1.2C/W unit if the case-to-heat-sink interface
is lubricated.
Note: When using a single supply, maximum transfer of heat away from the
LM1875 can be achieved by mounting the device directly to the heat
sink (tab is at ground potential); this avoids the use of a mica or other
type insulator.
The thermal requirements can become more difficult when
an amplifier is driving a reactive load. For a given magnitude
of load impedance, a higher degree of reactance will cause
a higher level of power dissipation within the amplifier. As a
general rule, the power dissipation of an amplifier driving a
60 reactive load (usually considered to be a worst-case
loudspeaker load) will be roughly that of the same amplifier
driving the resistive part of that load. For example, a loud-
speaker may at some frequency have an impedance with a
magnitude of 8
and a phase angle of 60. The real part of
this load will then be 4
, and the amplifier power dissipation
will roughly follow the curve of power dissipation with a 4
load.
LM1875
www.national.com
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| LM1876T | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
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