INA282, INA283
INA284, INA285
INA286
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SBOS485A –NOVEMBER 2009–REVISED JULY 2010
CURRENT DIFFERENCING
Occasionally, the need arises to confirm that the current into a load is identical to the current out of a load,
usually as part of diagnostic testing or fault detection. This situation requires precision current differencing, which
is the same as summing except that the two amplifiers have the inputs connected opposite of each other. Under
normal operating conditions, the final output is very close to the reference value and proportional to any current
difference. Figure 41 is an example of the connections required for current differencing.
First Circuit
Second Circuit
Supply
Load
VIN+
VIN-
VIN+
VIN-
Æ1
Æ2
Æ2
Æ1
Æ1
Æ2
Æ2
Æ1
Æ2
Æ2
Æ2
Æ2
Æ1
Æ1
Æ1
Æ1
Output
Output
Difference
Output
VREF
GND
GND
V+
V+
NOTE: This example is identical to the current summing example, except that the two shunt inputs are reversed in polarity,
this current differencing circuit is useful in detecting when current into and out of a load do not match.
Figure 41. Current Differencing Using an INA282 Family Device
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