Data Sheet

AD8417-2

THEORY OF OPERATION

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Rev. 0 | 10 of 15

The AD8417-2 is a single-supply, zero drift, difference amplifier

that uses a unique architecture to accurately amplify small differ-

ential current shunt voltages in the presence of rapidly changing

common-mode voltages.

The AD8417-2 design provides excellent common-mode rejection,

even with PWM common-mode inputs that can change at very fast

rates, for example, 1 V/ns. The AD8417-2 contains patented (U.S.

Patent 8,624,668 B2) technology to eliminate the negative effects of

such fast changing external common-mode variations.

The AD8417-2 features an input offset drift of less than 0.4 µV/°C.

This performance is achieved through a novel zero drift architecture

that does not compromise bandwidth, which is typically rated at

250 kHz.

The reference inputs, VREF1 and VREF2, are tied through 100 kΩ

resistors to the positive input of the main amplifier, which allows

the output offset to be adjusted anywhere in the output operating

range. The gain is 1 V/V from the reference pins to the output when

the reference pins are used in parallel. When the pins are used to

divide the supply, the gain is 0.5 V/V.

The AD8417-2 offers breakthrough performance without compro-

mising any of the robust application needs typical of solenoid

or motor control. The ability to reject PWM input common-mode

voltages and the zero drift architecture providing low offset and

offset drift allows the AD8417-2 to deliver total accuracy for these

demanding applications.