Common-mode difference amplifier with integrated precision matched resistors
Design & Manufacture
Linear Technology has introduced the LT6375, a unity-gain difference amplifier with integrated precision matched resistors, which precisely level shifts and buffers small difference signals while rejecting up to ±270V common mode.
The A-grade version achieves unprecedented performance: CMRR is 97dB (min), initial gain error is 35ppm (max), gain drift is 1ppm/C (max) and gain nonlinearity is 2ppm (max) with a common mode divide ratio of 25:1. The common mode divide ratio is selectable from 7:1 to 25:1, enabling the designer to select the ratio with the best performance for a given common mode input range.
At the heart of the LT6375 is a high precision Over-The-Top amplifier which operates with inputs both within and above the 3.3V to 50V supply voltage. This permits the combination of a wide input range and low voltage supply. Use of a low voltage supply limits power consumption and protects downstream circuitry from high voltage.
"The LT6375 combines a high precision, wide voltage range Over-The-Top amplifier with configurable precision matched resistors,” says Maziar Tavakoli, design manager, signal conditioning products. “With seven different divider ratios to choose from, precision, noise and speed can be optimized for specific input range requirements. For example, if the input common mode range is ±80V, a resistor divider ratio of seven may be selected to achieve lower noise, lower offset, and wider bandwidth than is achievable with a ratio of 20.”
The LT6375 includes many other useful features, including rail-to-rail outputs, low supply current and a shutdown mode. It is available in a 4mm x 4mm 12-lead DFN and a 4mm long MSOP package with 12 leads. Both packages include skipped leads for extra spacing of high-voltage input signals.
The LT6375 is fully specified over the -40C to 85C (I-grade) and -40C to 125C (H-grade) temperature ranges.