250-mA audio buffer offers low distortion, noise

National Semiconductor has announced the LME49600 high-fidelity high-current audio buffer – offered as the lowest noise and distortion such device for professional and high-performance audio applications. Designed for use inside an op amp's feedback loop and capable of continuously sourcing or sinking 250 mA, the LME49600 increases output current, improves capacitive load drive and eliminates thermal feedback.

Part of National's LME audio amplifier family, the buffer can deliver the necessary output current to drive multiple low-impedance headphones and the voltage swing to drive several high-impedance headphones. Other applications include line drivers, ADC input drivers, low-noise and wide-frequency voltage regulators, as well as driving the headphone amplifier output stage in mixer consoles and capacitive loads in low-power audio amplifiers.

A pin-selectable bandwidth feature includes a low-current, 30-MHz bandwidth-mode that consumes 8 mA and a 180-MHz bandwidth-mode that consumes 15 mA. Bandwidth is adjusted by either leaving the bandwidth-control pin unconnected or by connecting a resistor between the bandwidth pin and the emitter voltage pin.

In both modes, the LME49600 has a nominal 2,000 V/µs slew rate. Other specifications include an input referred voltage noise density of 2.6 nV/√Hz and a supply voltage range of ±2.25V to ±18V.

In a closed-loop configuration with National's LME49710 single op amp, THD+N is only 0.00003%. Combining the LME49600's ±250-mA output current capacity with the LME49710 and an LM4040 low-noise bandgap reference produces a very high-performance, low-noise, wide-bandwidth, audiophile quality, voltage regulator.

The LME49600 was developed using the company's VIP3 high-voltage, high-performance, complementary bipolar technology, with vertically integrated NPN and PNP transistors, which enables larger peak-to-peak output voltage swings that suit high-voltage requirements in high-end audio applications. The LME49600 is fully protected through internal current limit and a thermal shutdown that activates when the junction temperature exceeds 150ºC.

Pricing and availability: The LME49600 is available now in a 5-lead TO-263 surface mount package and is priced at $4.50 each in 1000-unit quantities.

National Semiconductor , 1-800-272-9959,

Related links:
LME49600 data page
LME49600 data sheet (PDF)

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