High precision fixed gain fully differential amplifiers

The precision resistors, which are integrated in LTC6363-0.5, LTC6363-1 and LTC6363-2, have been designed with overall system performance in mind, striking a balance between noise and linearity, and utilising laser trimmed factory calibration to achieve a level of precision which is difficult and costly to achieve discretely. 

Initial gain accuracy is 45ppm maximum and varies by only 0.5ppm/oC maximum over temperature. Common mode rejection ratio, which is typically limited by discrete resistor matching, is an outstanding 94dB minimum, equivalent to a 0.002% resistor matching.

Maziar Tavakoli, Design Manager, Linear Products and Solutions, stated: “One of the challenges when driving high performance SAR ADCs is finding an appropriate driver that consumes comparable power while maintaining the noise and linearity performance of the ADC. This is where the LTC6363 family excels. For example, the LTC2378-20 20-bit SAR ADC consumes 21mW at 1Msps. 

“The LTC6363 family’s noise and linearity have negligible impact on ADC performance while consuming a mere 19mW, comparable to the ADC’s power consumption. Now with the LTC6363-0.5, LTC6363-1 and LTC6363-2 you can get this same ADC driving performance plus the added precision afforded by the precision integrated resistors, all in the same compact MSOP8 package.”

The entire LTC6363 family operates with supply voltages from 2.8 (±1.4) to 11V (±5.5V) while drawing 1.75mA typical supply current. The devices are specified for operation over a temperature range from -40 to +125°C. The LTC6363 fixed-gain series are available in a three by five millimetre plastic MSOP8 package, and the LTC6363 (without resistors) is also offered in the tiny two by three millimetre DFN package.