Product category:
Analogue and Mixed Signal ICs
News Release from: National Semiconductor | Subject: LM4702
Edited by the Electronicstalk Editorial
Team on 21 September 2006
Driver powers up high-end audio
National Semiconductor has introduced the industry's first integrated, 200V stereo driver for high-power amplifiers.
National Semiconductor has introduced the industry's first integrated, 200V stereo driver for high-power amplifiers The LM4702, the first member of a new high-performance audio family, is available in three grades, all with mute functions, to suit a variety of demanding consumer and professional audio applications
This article was originally published on Electronicstalk on 5 Jan 2001 at 8.00am (UK)
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The LM4702 is a monolithic, output stage driver optimised for high supply voltages.
Its three grades differ by operating voltage level, performance specification and guarantee.
The LM4702C targets high-volume applications, such as stereo systems and audio/visual (AV) receivers.
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The LM4702B includes a higher voltage rating of plus and minus 20V to 100V, along with tighter specifications, for high-end audio, guitar amplifiers, professional audio amplifiers and high-fidelity-powered speakers.
For ultra-high-end consumer and professional audio, the LM4702A is fully specified, with all limits tested and guaranteed over voltage and temperature from +/-20 to 100V.
It is offered in a military 883-compliant, gold-plated TO-3 package.
The LM4702's completely integrated power amplifier driver eliminates the need to design a discrete amplifier, often a time-intensive part of a power amplifier project.
This allows the designer to focus on the output-power stage design that is scalable over a wide range of power levels and applications ranging from 50W AV receivers to 500W amplifiers.
In addition to saving design time, the LM4702 saves board space by eliminating many equivalent high-voltage discrete components.
While a single LM4702 replaces a stereo pair of discrete drivers, multiple LM4702s can be used for multi-channel surround-sound applications.
Since the LM4702 has an extremely high operating voltage, low-cost, unregulated power supplies can be used while still maintaining adequate voltage headroom in high-line conditions.
National's LM4702 is a stereo audio amplifier driver designed to drive high-power discrete transistors, or Darlington pairs, in systems delivering 25W per channel to more than 300W per channel.
When implemented in a complete amplifier as shown in reference design AN-1490 (available from the National website), the total harmonic distortion plus noise (THD+N) is 0.0006% into an 8ohm load.
The amplifier's output power is scaled by changing the supply voltage and corresponding output power transistors.
For higher current and power levels, the output transistors can be configured in parallel without changing the basic LM4702 driver circuit.
To prevent long-term thermal stress, the LM4702 has a sophisticated thermal protection scheme that is activated when the die temperature exceeds 150C.
The driver's transparent, no-click, no-pop mute function forces the amplifier output into a quiescent state, saving power.
National engineers developed the LM4702 using a proprietary process technology.
The high-voltage, high-performance, complementary bipolar technology, with vertically integrated NPN and PNP transistors, enables larger peak-to-peak output voltage swings that are well-suited for high-voltage requirements in high-end audio applications.
Available now in a 15-lead TO-220 package, the LM4702C is priced at US $4.50 in 1000-unit quantities.
The LM4702A is priced at $125 and the LM4702B is priced at $14.95, both in 100-unit quantities.
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