AD8475:  Precision, Selectable Gain, Fully Differential Funnel Amp

The AD8475 is a fully differential, attenuating amplifier with integrated precision gain resistors. It provides precision attenuation (by 0.4 or 0.8), common-mode level shifting, and single-ended-to-differential conversion along with input overvoltage protection. Power dissipation on a single 5 V supply is only 16 mW.

The AD8475 is a simple to use, fully integrated precision gain block, designed to process signal levels of up to ±10 V on a single supply. It provides a complete interface to make industrial level signals directly compatible with the differential input ranges of low voltage, high performance 16-bit or 18-bit single-supply successive approximation (SAR) analog-to-digital converters (ADCs).

The AD8475 comes with two standard pin-selectable gain options: 0.4 and 0.8. The gain of the part is set by driving the input pin corresponding to the appropriate gain.

The AD8475 also provides overvoltage protection from large industrial input voltages up to ±15 V while operating on a single 5 V supply. The VOCM pin adjusts the output voltage common mode for precision level shifting, to match the ADC’s input range and maximize dynamic range. The AD8475 works extremely well with SAR, Σ-Δ, and pipeline converters. The high current output stage of the part allows it to drive the switched capacitor front-end circuits of many ADCs with minimal error.

Unlike many differential drivers in the market, the AD8475 is a high precision amplifier. With 500 μV maximum output offset, 10 nV/√Hz output noise, and −112 dB THD + N, the AD8475 pairs well with high accuracy converters. Considering its low power consumption and high precision, the slew-enhanced AD8475 has excellent speed, settling to 18-bit precision for 4 MSPS acquisition.

The AD8475 is available in a space-saving 10-lead MSOP package. It is fully specified over the −40°C to +85°C temperature range.

• ADC driver
• Differential instrumentation amplifier building block
• Single-ended-to-differential converter