Zero-crossover op amp delivers glitch-free performance

Dallas&#8212Proclaiming a step advance for high-performance operational amplifiers, Texas Instruments' OPA365 utilizes a zero-crossover input architecture to achieve glitchless rail-to-rail performance for precision data conversion applications. With a total harmonic distortion (THD + N) of just 0.0006 percent, low noise (4.5nV/Hz1/2 ) and gain bandwidth of 50 MHz, the single-supply OPA365 is suited for portable instrumentation, data acquisition, test and measurement, audio, and portable medical systems.

“The OPA365 leverages TI's expertise in analog signal conditioning to solve the common design challenge of finding an op amp that does not limit the capability of the data converter,” said Art George, senior vice president of the High-Performance Analog business.
Suited for use with the company's ADS8327, ADS8361, ADS7886 analog-to-digital chips, DAC8811 and DAC8830 digital-to-analog converters, and precision voltage references such as REF32xx, the OPA365 is designed to provide customers with a state-of-the-art solution for precision applications. It's also optimized to work with TMS320 DSP platforms.

The OPA365's single-stage input section handles rail-to-rail input signals without the crossover distortion associated with traditional two-stage complementary input topologies, explained Tadija Janjic, product line manager for Precision Linear Products. “We replace the op amp's complementary stage with a charge pump that biases Vin above the Vin using the traditional topology, he said. “So the input stage is constantly on, and there's no change in offset voltage.” As a result, the harmonics generated during crossover in an op using the typical two-stage topology are largely eliminated with the OPA365. The technique was first applied two years ago in the company's OPA364 op amp. In that context, the OPA365 is a next-generation device with a better charge pump, largely by virtue of the company's relatively new HPL7 CMOS process, says Janjic.

As for performance, the design boosts the common-mode rejection ratio (CMRR) to 100 dB minimum and 120 dB typical over the entire input range (100 mV beyond the supply rails) without compromising differential linearity. The op amp features a settling time of 300 ns to 0.01 percent, low offset voltage (200 microvolts maximum), and single-supply operation from 2.2 to 5.5 volts.

Click here for the product datasheet. For more information on complete analog design support, and to download the latest Amplifier & Data Converter Selection Guide, click here. The OPA365, in a SOT23-5 package, has a suggested resale price of 95 cents in 1k quantities. The op amp will be available in an SO-8 package in 3Q. A dual version of this op amp, the OPA2365, will also be available in 3Q in DFN-8 and SO-8 packages. All devices are specified for operation from -40 to +125&degC.

Texas Instruments , 1-800-477-8924,

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