Twenty-five years after National Semiconductor Corp designed the basic Op-Amp, or operational amplifier that to this day still provides thousands of system engineers and millions of appliances with reasonably-priced supply voltages from 5V to 32V, the company has re-invented the op-amp to provide extremely low voltage, low cost devices in tiny packages. NatSemi has introduced the LMV300 family , the first product of which is the LMV321, a single op-amp in a SC70-5 package, which measures about 3/32 inch square. The family also includes the dual op-amp LMV358 and the quad LMV324. All three devices are single supply rail-to-rail output operational amplifiers with no crossover distortion – a problem which until now has made the op-amp only adequate for use in for example sound systems in personal computers. The company says it is focusing strongly on the information industry now, with the increasing number and variety of devices that will interface with the information highway. The 25-year old LMV324 op-amp has been just good enough to do the job that many of the current devices require, according to Seamus Coyle NatSemi’s senior technical marketing manager. The drivers now for these analogue signal amplifiers are the same as those in the digital world, the proliferation of smaller, cheaper, portable consumer devices, many of which will be battery-powered, and which need therefore to be low voltage, as small as possible and low cost. Also integration is an increasing issue. While discreet op-amps are still in demand, particularly in the US, European manufacturers, particularly mobile phone makers such as LM Ericsson Telefon AB and Nokia Oy, have achieved a high level of integration. What has enables the complete re-design of the op-amp is the availability of advanced sub-micron silicon-gate BiCMOS processes, which combine the speed of bipolar and the low power of CMOS, while keeping the costs down. Coyle says even one year ago, this technology was not available to the company. The new op-amp family will be pin compatible with the old, and the company says externally, engineers will not notice any difference in the product, it will be familiar and they won’t need to change their design concepts. NatSemi says it has no intention of obsoleting the 25-year old stalwart LMV324, but recognizes that once customers go over to the new op-amps, they will obsolete them for their own business. However, Coyle says there are still plenty of industrial applications that continue to need higher voltage, and where performance, rather than size, is the main requirement. The company’s road-map includes going to an even smaller form factor, where there will be no leads on the package at all, as well as a higher voltage device using the new processes. With the new processes, the company can get a staggering 80,000 dies on a single 6 wafer. This compares to the usual 5,000 to 6,000. There is still a lot of spare space on the silicon, and NatSemi has managed to reduce the size of resistors, and integrate them into the SOT casing with the op-amp, thus saving designers even more space. The company will offer custom build of this low level integration for manufacturers looking for very large volume builds. It is also working on other components using the same processes, such as analogue to digital converters, and is likely to integrate these components in the future. With the new technology the door is now wide open, Coyle says, and in particular the whole of the portable market from cell phones to personal digital assistants is open to the company. The op-amps are now in full production at NatSemi’s South Portland, Maine plant.
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