Analog Angle Article

Differential op amp tackles CMV to +275V, offers CMRR of 100 dB

Dallas, Texas–Op amps, those versatile building blocks of the analog world, already come in thousands of varieties. Still, there's always a need for more and better, where “better” means having more of various desired attributes without degradation of others.

The INA149 differential amplifier (aka diff amp–a specialized type of op amp) from Texas Instruments demonstrates this point. With high common-mode-voltage tolerance and rejection, it can be used for applications such as such as high-voltage current sensing; battery-cell voltage monitoring in photovoltaic, telecom, electric vehicles; alternative energy applications; power-supply current monitoring; and motor control.

The vendor claims this is industry’s most accurate difference amplifier for high common-mode voltage applications up to + 275 V, and makes some other strong competitive claims, as well:

  • 100-dB CMRR with a specified minimum CMRR of more than 90 dB throughout the industrial temperature range of -40°C up to 125°C increases overall measurement accuracy more than two-fold compared to the closest competitor.
  • Extended input common-mode-voltage from -275 V to +275 V enables accurate monitoring of signals riding in high common-mode voltages, eliminating the need for multiple supply sources and analog isolation components to interface to an analog-to-digital converter (ADC).
  • Twice the slew rate and full-power bandwidth of its closest competitor for applications where abrupt changes, such as short circuit conditions, are monitored and corrective actions need to be commanded quickly. The faster response and wider large-signal bandwidth of 500 kHz increases system performance.
  • Lower maximum initial-gain error of 0.02 % provides better accuracy, especially in applications with lower common-mode voltage signals.

Tools and support: TI offers a variety of tools and support including the INA149EVM evaluation module ($49), and a TINA-TI SPICE model to simulate device performance.

Availability, packaging and pricing: The INA149 is available today in a 4.9-mm × 6-mm SOIC package, priced at $2.70 (1,000-unit quantities).

For more information: go to .

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