Shrinking mirophone amplifiers boost performance

National Semiconductor has two new amplifiers it says dramatically improve audio performance by replacing existing microphone technology with a revolutionary design solution.

National Semiconductor has two new amplifiers it says dramatically improve audio performance by replacing existing microphone technology with a revolutionary design solution.

The LMV1012 and LMV1014 are the market's first "amps in a mic", integrated directly inside two- and three-wire electret condenser microphones (ECMs).

These amplifiers replace the junction field effect transistor (JFET), for longer battery life and greater noise immunity, resulting in better microphone performance.

These products are ideal for use in microphones in mobile handsets, headset accessories and other portable microphone applications.

"These new products place National Semiconductor in a leading position in terms of capturing designs, particularly in the handset space", said Susan Inouye, Senior Industry Analyst at Databeans in Reno, Nevada.

"Handset production continues to migrate to lower cost manufacturing regions, increasing the importance of lower component count and simplicity of production".

"With National Semiconductor's amplifiers, which can be integrated directly into the ECM, BSE is able to create higher sensitivity microphones which significantly improve audio performance in applications like mobile phones and other communications devices", said Kingly Bang, Corporate Marketing Manager with BSE Corporation, a leading Korean microphone manufacturer.

"To optimise today's microphones, careful board design and other filtering components are necessary", said Dennis Swan, Marketing Manager for National's Amplifier Products Group.

"Also, until recently, the resulting packaged chip size did not allow amplifiers to fit into the increasingly smaller-sized ECMs.

National recognised that a combination of innovative circuit design and packaging technology would make significant improvements to properties such as sensitivity, distortion and supply current, enabling ECMs with greatly improved performance and battery life".

National Semiconductor's LMV1012 is an amplifier for two-wire ECMs.

The built-in gain of 17dBV has been optimised for handset microphones.

Additional benefits of the LMV1012 are improved RF immunity and low distortion.

New ECMs using the LMV1012 offer THD of 0.1%, SNR greater than 55dB and supply current less than 240uA.

Applications for high-gain microphones include mobile communications, automotive accessories, cellular phones and PDAs.

The LMV1014 is an amplifier for three-wire, low current and low noise ECMs.

This product draws a supply current of less than 40uA while providing a low output impedance of 200ohm.

The LMV1014 provides a high power supply rejection ratio (PSRR) greater than 60dB and an SNR of greater than 55dB.

This device is designed for applications requiring low supply current and high noise immunity, such as Bluetooth wireless technology communication products, microphone accessory products, handheld recording devices and PDAs.

Both amplifiers are fully compatible with existing ECM standards.

The LMV1012 is available now in 4-bump micro SMD packaging and is priced at $0.39.

The LMV1014, available now in 4-bump micro SMD packaging, is priced at $0.49.

Both prices are in 1000-unit quantities.

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