Amp gains a first

Analog Devices’ new AD628 is claimed to be the first common-mode difference amplifier to include programmable gain.

Using an external resistor, the AD628 can be adjusted to provide a gain range from 0.1 to 1000. It is designed to accept +/-140 V inputs and drive the newest generation of single supply analog-to-digital or sigma-delta converters.

Additionally, a dedicated output amplifier allows the designer to attenuate, level shift, filter, and scale the output signal – functions that up to this point were only available with discrete components. The AD628 can also convert a bipolar input signal to a unipolar output.

The AD628 provides 80 dB of common-mode rejection from dc to 500 Hz (min). It operates from either single or dual supplies from 5 to 15V. It also allows the user to filter out noise by adding a single external capacitor to make a single pole filter.

The AD628 is suitable for many industrial applications, particularly those accepting inputs from various sensors, motor drive interfaces and controllers, high voltage current sensing, and sensor signal conditioning applications. The high common-mode input impedance also makes the AD628 ideal for high voltage measurements across a shunt resistor.

The AD628 is packaged in an 8-lead SOIC and 8-lead microSOIC, and is rated to work over the industrial temperature range, -40 degrees C to +85 degrees C. Samples are available now. Analog Devices estimate that using the AD628, which is priced at $3.45 per unit in 1,000-piece quantities, will cost less than half the price of implementing a discrete solution.

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