LM1875T/NOPB National Semiconductor, LM1875T/NOPB Datasheet - Page 7

IC AMP AUDIO PWR 30W AB TO220-5

LM1875T/NOPB

Manufacturer Part Number
LM1875T/NOPB
Description
IC AMP AUDIO PWR 30W AB TO220-5
Manufacturer
National Semiconductor
Type
Class ABr
Datasheets

Specifications of LM1875T/NOPB

Output Type
1-Channel (Mono)
Max Output Power X Channels @ Load
30W x 1 @ 8 Ohm
Voltage - Supply
16 V ~ 60 V, ±8 V ~ 30 V
Features
Short-Circuit and Thermal Protection
Mounting Type
Through Hole
Package / Case
TO-220-5 (Bent and Staggered Leads)
Amplifier Type
Audio
Bandwidth
70 kHz (Power), 5.5 MHz (Gain)
Current, Input Bias
±0.2 μA
Current, Input Offset
0 mA
Current, Supply
70 mA
Harmonic Distortion
0.015 %
Open Loop Gain
90
Package Type
TO220-5
Slew Rate
8
Voltage, Input
-25 to +25 V
Voltage, Input Offset
±1 mV
Voltage, Noise
3 μV
Voltage, Supply
16 to 60 V
Amplifier Class
B
No. Of Channels
1
Output Power
25W
Supply Voltage Range
16V To 60V
Load Impedance
8ohm
Operating Temperature Range
0°C To +150°C
Amplifier Case Style
TO-220
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
*LM1875T
*LM1875T/NOPB
LM1875
LM1875T

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Part Number
Manufacturer
Quantity
Price
Part Number:
LM1875T/NOPB
Manufacturer:
National Semiconductor
Quantity:
35 635
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Manufacturer:
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Quantity:
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Part Number:
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Application Hints
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 8Ω, it can develop up to
19W of internal power dissipation. If the die temperature is to
remain below 150˚C for ambient temperatures up to 70˚C,
the total junction-to-ambient thermal resistance must be less
than
Using θ
thermal resistance and the heat-sink-to-ambient thermal re-
sistance must be less than 2.2˚C/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 1˚C/W if lubricated, and about 1.2˚C/W if dry.
If a mica insulator is used, the thermal resistance will be
about 1.6˚C/W lubricated and 3.4˚C/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
JC
=2˚C/W, the sum of the case-to-heat-sink interface
(Continued)
7
4.2˚C/W−2˚C/W−1.6˚C/W=0.6˚C/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 50˚C (122˚F), resulting in a 1.6˚C/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 1.2˚C/W unit if the case-to-heat-sink interface
is lubricated.
Note: When using a single supply, maximum transfer of heat away from the
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 8Ω and a phase angle of 60˚. The real part of
this load will then be 4Ω, and the amplifier power dissipation
will roughly follow the curve of power dissipation with a 4Ω
load.
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.
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