True differential converters can offer many advantages
over single-ended input A/D Converters (ADC). In addi-
tion to their common mode rejection ability, these con-
verters can also be used to overcome many DC biasing
limitations of common signal conditioning circuits.
Listed below are some typical application issues that
can be solved with proper biasing of a differential con-
verter:
• Limited output swing of amplifiers
• Unwanted DC-bias point
• Low level noise riding on ground
• Unwanted or changing common mode level of
input signal
This application note discusses differential input config-
urations and their operation, circuits to implement
these input modes and techniques in choosing the cor-
rect voltage levels to overcome the previously
mentioned challenges.M AN842
Differential ADC Biasing Techniques, Tips and Tricks
It is important to note that the converter output is zero
Author: Craig L. King when the inputs are equal. As the voltage difference
Microchip Technology Inc. between IN+ and IN- increases, the output code also
increases. The maximum voltage at which digital code
INTRODUCTION saturation will occur is VREF. The differential conver-
……
