Differential op amp tackles common-mode voltage as high as ±275V

Bill Schweber, EE Times -- EDN, January 19, 2012

Op amps, those versatile building blocks of the analog world, come in thousands of varieties. Yet there’s still a need for more and better, in which “better” means units with more desired attributes but not at the expense of others. One such amplifier is Texas Instruments’ INA149 differential amplifier. With common-mode voltage as high as ±275V and 100-dB CMRR, the device finds use in high-voltage current sensing; battery-cell-voltage monitoring in photovoltaic, telecom, and electric-vehicle applications; alternative-energy applications; power-supply-current monitoring; and motor control.

The vendor claims that the device’s CMRR, along with a specified minimum CMRR of more than 90 dB throughout the industrial temperature range of −40 to +125°C, provides two-times better overall measurement accuracy than that of its closest competitor. An extended input-common-mode voltage of −275 to +275V 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 ADC. The unit also offers twice the slew rate and full-power bandwidth of its closest competitor for applications requiring the monitoring and quick correction of abrupt changes, such as short-circuit conditions. The faster response and wider large-signal bandwidth of 500 kHz increase system performance. The INA149’s maximum initial gain error of 0.02% provides accuracy, especially in applications with low common-mode-voltage signals.

TI offers a variety of tools and support, including the $49 INA149EVM (evaluation module) and a Tina-TI Spice model to simulate device performance. The INA149 comes in a 4.9×6-mm SOIC package and sells for $2.70 (1000).

Texas Instruments