BeagleBone Black Interfacing: hardware and software by Magda Yury

Author:Magda, Yury
Language: eng
Format: epub, azw3
Publisher: Yury Magda
Published: 2014-11-21T16:00:00+00:00

Note that the REF pin should be tied to a low impedance point for optimal common-mode rejection (CMR), so don’t connect the resistive divider formed by R1 directly to the REF pin. In our circuit, the voltage from the divider R1 is fed to pin 5 of op-amp OPA364. The voltage follower formed by the op-amp OPA364 acts as a buffer providing very low output impedance suitable for REF. The potentiometer R1 should be of high precision and have the impedance from a few tens of Ohms to several KOhms.

You can take any general purpose single supply op-amp (OPA348, OPA248, MCP601, MCP6021, etc.) in the voltage follower circuit. But, remember, in order to process bipolar input signals you need to select the proper VREF voltage so that to avoid the distortion of input signals.

Some words about powering the in-amp AD623. The power supply is connected to +VS and –VS terminals. The supply can be either bipolar (VS = ±2.5V to ±6V) or single supply (-VS = 0V, +VS = 3.0V to 12V). Power supplies should be capacitively decoupled close to the power pins of the device. For the best results, use surface-mount 0.1 µF ceramic chip capacitors and 10 µF electrolytic tantalum capacitors.

For better understanding a device, it would be worth learning the AD623 datasheet before the in-amp is put in the circuit.

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