National Semiconductor says its LM4867 Boomer amplifier is the world's first truly noise-free 2.1W stereo amplifier with headphone mode

Featuring National's patent-pending technology, the LM4867 provides popless, clickless operation, meaning that there are no sound artifacts when the amplifier is turned on or off. This product is ideal for a number of portable audio systems, including notebook computers and PDAs, as well as desktop computer applications.

This article was originally published on Electronicstalk on 1 March 2001 at 8.00am (UK)
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"Not only does the new circuit topology of the LM4867 eliminate unnecessary popping, clicking and general noise typically associated with Class AB amplifiers, but it also eliminates the need for expensive headphone output coupling capacitors, providing significant cost and space savings to the customer", said Steve Kaufman, marketing manager for National's audio amplifier product group.

"The LM4867 offers the market's only completely noise-free solution in a small package at a competitive price".

National's LM4867 is a dual bridge-connected audio power amplifier which, when connected to a 5V supply, will deliver 2.1W to a 4ohm load or 2.4W to a 3ohm load with less than 1.0% THD+N.

The LM4867 uses patent-pending technology to eliminate all traces of clicks and pops when the supply voltage is first applied.

The amplifier also has a headphone mode sense input pin, which is used to switch the amplifiers from bridge to single-ended mode for driving headphones.

A new circuit topology in the LM4867 eliminates headphone output coupling capacitors, and a MUX control pin allows selection between the two sets of stereo input signals.

The MUX control can also be used to select between two different customer-specified closed-loop responses.

In order to simplify audio system design, National's LM4867 Boomer amplifier combines dual bridge speaker amplifiers and stereo headphone amplifiers in one package.

The LM4867 also features an externally controlled power-saving micropower shutdown mode, a stereo headphone amplifier mode and thermal shutdown protection.

Available immediate, the LM4867 is available in LLP, TSSOP and exposed-DAP TSSOP packaging.