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Op amps amplify low-level analog signals simply

Posted: 24 Apr 2006 ?? ?Print Version ?Bookmark and Share

Keywords:op amp? ADC? analog-to-digital converter? Cirrus? Bettyann Liotta?

Cirrus is launching this family of op amps with four partstwo single and two dual versions. The op amps are a result of the company's effort to develop amps that can support their own analog-to-digital converters (ADCs), which are the highest resolution, and lowest noise in the industry, according to Rich Wegner, senior marketing manager of Cirrus' industrial product division. "We want the amplifier to contribute as little error as possiblebut it has to be able to provide enough gain to preserve measurement accuracy," he said.

Typically, the ADC always performs better than the amplifier so you end up chasing your tail to find an op amp that can maintain the ADC's specs, Wegner said. These latest amplifiers originated from the front end of Cirrus' six-year-old CS5532 ADC family.

When comparing these devices to competing devices, designers need to look at the whole picture for total accuracy instead of doing a spec to spec comparison, Wegner said. "You need a combination of gain, low voltage noise, and low offset drift to achieve low total error for high resolution ADCs," he said. "Otherwise, you'll need additional parts to correct certain parameters," he added.

Three years ago, Cirrus rolled out its last generation family (CS3001/3002, CS3011/3012) of precision amps. The devices are similar to the new ones with the exception of two key specspower consumption, which has been lowered significantly from 1,400A to 500A, and noise performance, which has increased a bit in the newer family, according to Wegner. "There is a slight tradeoff since we lowered power consumptionnoise performance has increased from 11nV to 17nV in the newer family. Essentially, noise is up by a factor of two and power consumption is down by a factor of two, which is a reasonable tradeoff in portable applications," he said.

Although the package size of the new and older op amps is the same right now (SO8), the company plans to roll the devices out in the new leadless QFN package size in June (4-by-4mm). "This represents a 50 percentage reduction in acreage," Wegner said.

- Bettyann Liotta

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