Circuit Note CN-0251 is a flexible 4-channel analog front end for wide dynamic range signal conditioning. The circuit is designed and built by Analog Devices engineers and has been tested and verified. It includes devices such as multiplexers, instrumentation amplifiers, amplifiers, and ADCs.
This document presents Circuit Note CN-0251, a flexible signal conditioning circuit designed for processing signals with a wide dynamic range, varying from several millivolts to 20 V peak-to-peak. The circuit integrates an ADG1409 multiplexer, an AD8226 instrumentation amplifier, an AD8475 differential attenuating amplifier, an AD7192 24-bit sigma-delta ADC, and an ADR444 reference.
The design addresses challenges in industrial automation and process control by providing programmable gain, high common-mode rejection, and high input impedance. It allows for the attenuation and level shifting of large signals (e.g., +10 V) while amplifying small signals to maximize the dynamic range of the ADC. The document details the circuit function, component selection, gain configurations, and system performance metrics.
| Input Signal Range | several mV p-p to 20 V p-p |
|---|---|
| ADC Resolution | 24-bit sigma-delta |
| Common-Mode Rejection (AD8226) | up to 80 dB |
| Input Impedance (AD8226) | 800 MO differential mode |
| AD8475 Gain Options | 0.4 or 0.8 |
| Antialiasing Filter Cutoff | 800 Hz |
| Common-Mode Filter Cutoff | 160 kHz |
| Peak-to-Peak Noise | approximately 3.9 µV |
| RMS Noise | 860 nV |
The circuit can be used in industrial automation, process control, instrumentation, and medical equipment applications.
The circuit processes signals varying from several mV p-p to 20 V p-p.
The external Re resistor is omitted, setting the gain of the in-amp stage to 1.