LT1997 Gain Selectable Funnel Amplifiers

Analog Devices' LT1997-2 is an attenuating (funnel) difference amplifier that can be used to translate large differential signals to the low voltage range compatible with ADCs. The LT1997-3 combines a precision operational amplifier with highly-matched resistors to form a one-chip solution for accurately amplifying voltages.

The LT1997-2 combines a precision operational amplifier with highly-matched resistors to form a one-chip solution to attenuate and level shift voltages accurately using no external components. It comes with three standard pin-selectable gain options (0.1, 0.2, and 0.25), which can be further combined to form gains from 0.0455 to 0.55 (attenuations of 1.82 to 22) with accuracy of 0.006% (60 ppm). The LT1997-2 also works across a very wide input common-mode voltage range (±255 V), enabling robust operation in demanding industrial environments. Its excellent resistor matching results in a common mode rejection ratio of greater than 105 dB.

The LT1997-3 is particularly well suited for use as a difference amplifier, where the excellent resistor matching results in a common mode rejection ratio of greater than 91dB. The amplifier features a 60 μV maximum input offset voltage and a -3 dB bandwidth of 1.1 MHz (gain = 1). The LT1997-3 operates from any supply voltage from 3.3 V to 50 V and draws only 350 μA supply current. The output typically swings to within 100 mV of either supply rail.

The LT1997 is fully specified at 5 V and ±15 V supplies and from -40°C to +125°C. These devices are available in 16-lead MSOP and 4 mm × 4 mm DFN14 packages. The LT1997 is ideal for high side low sensing, ADC drivers, and industrial data-acquisition front-ends.