audio/videoZONE Products for the week of November 11, 2002
National Semiconductor Says . . .
LMV1012/1014: Amplifiers Improve Audio Performance
And Sensitivity In Microphones
"Amp in a Mic" Transforms Market by Replacing Decades-Old
Technology
National Semiconductor Corporation announced two new amplifiers that 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 2- and 3-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 Inc, 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.
analogZone Says . . .
We don't see many truly innovative product introductions in any year - at least not ones that are going to make money - but these products from National break a barrier that has existed for decades. The electret condenser microphone is in just about every portable appliance manufactured today - and in many other applications as well. Volumes shipped are in nine figures every year and although the costs of manufacturing the products have been addressed many times, and sizes have been reduced to as low as 2 mm in height, the actual technology has remained substantially unchanged.
Smaller IC packages now make it possible to change that by replacing the JFET buffer (separating the capacitor element from the output load) with a true amplifier. Getting gain at this point reduces the design problems on the circuit board, reduces the care needed with extraneous noise, improves the sensitivity and improves the SNR.
The two versions of the microphone amplifier are as a direct replacement for existing JFETs and a version that offers substantial improvement by adding an extra connection.
Conventional powering of electrets by phantom power through a small load resistor in the output is the most common connection and the LMV1012, although limited by this arrangement, directly replaces the JFET and offers a typical voltage gain of 15.6 dB with THD down at 0.09%, SNR (A-weighted) at 60 dB; with a supply between 2 and 5 V the quiescent is about 186 µA. The size necessary for a physical replacement of the JFET is achieved with National's micro-SMD packaging, in this case a 4-bump package.
PSRR and performance can be improved still further by separating the power feed from the output line - i.e. no longer a phantom feed - by adding an additional connection to the microphone. The LMV1014 reduces quiescent down to 38 µA, a dramatic reduction, while PSRR is at 88 dB. 6 dB of gain is offered. The LMV1014 is also in a 4-bump microSMD.
These are truly innovative approaches to an old design and will be rapidly adopted by the industry. Pricing has been set so that replacing the current plastic packaged JFETs will not be a financial burden and that will further speed adoption. My hat is off to National for this jump forward. There are also implications with this technology in professional microphones providing gain much closer to the capacitor element.
Both parts are available now in 4-bump microSMD with the LMV1012 priced
at $0.39 and the LMV1014 at $0.49, both in 1000-piece lots. National provided
analogZONE with data sheets but at publication deadline the Web location
of a restricted version of the sheets was unknown. Check their informational page.