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National rolls out 'first' 200V stereo driver

Posted: 27 Sep 2006 ?? ?Print Version ?Bookmark and Share

Keywords:National Semiconductor? LM4702? LM4702C? LM4702B? LM4702A?

National's LM4702 stereo driver

National Semiconductor Corp. has introduced an integrated 200V stereo driver for high-power amplifiers, said to be the first in the industry. The LM4702, the first member of a high-performance audio family, is available in three grades, all with mute functions to suit a variety of demanding consumer and professional audio applications, the company said.

LM4702 is a monolithic, output stage driver designed 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 A/V receivers. The LM4702B includes a higher voltage rating of 20-100V, along with tighter specifications, for high-end audio, guitar amplifiers, professional audio amplifiers and high-fidelity-powered speakers. For ultrahigh-end consumer and professional audio, the LM4702A is fully specified with all limits tested and guaranteed over voltage and temperature from 20V to 100V. It is offered in a military 883-compliant, gold-plated TO-3 package.

Integrated power amp
The LM4702's 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, the company said, ranging from 50W A/V receivers to 500W amplifiers. The device also saves board space by eliminating many equivalent high-voltage discrete components, the company added.

While a single LM4702 replaces a stereo pair of discrete drivers, several of these devices can be used for multichannel surround-sound applications. Since the device has a high operating voltage, low-cost and unregulated power supplies can be used while still maintaining adequate voltage headroom in high-line conditions.

This stereo audio amplifier driver is 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, THD+N is 0.0006 percent into an 8-ohm 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 driver circuit.

Thermal protection
To prevent long-term thermal stress, the device 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.

Available today in a 15-lead TO-220 package, the LM4702C is priced at $4.50 in 1,000-unit quantities. The LM4702B is priced at $24.95 in 100-unit quantities. The LM4702A is priced at $150 in 25-unit quantities and will be available in January 2007.




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Related Datasheets
Part Number Description Category
? LM4702 Stereo High Fidelity 200 Volt Driver with Mute Passives - Filters, Oscillators and Resonators

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