High-Side Sense Difference Amplifier

Application

This circuit demonstrates the AD626 as a high-side current-sense style difference amplifier, where the measured signal is the small voltage between two elevated input nodes.

Schematic

The high-side input sources sit in the same source row as the rails, all returns share one lower bus, and the measured output/load is on the right. GND, FILTER, and G100 are tied to the reference bus for a stable baseline operating point.

Design Context

VIN+ is 5.10 V and VIN- is 5.00 V, representing a 100 mV sense voltage riding on a 5 V common-mode level. The split rails give the macro-model enough headroom while the output is measured against the shared return.

Expected Behavior

The operating-point table should show the elevated input pair and a ground-referenced output that changes with the 100 mV input difference.

Key Values

• VCC / VEE: +15 V and -15 V.
• High-side inputs: 5.10 V and 5.00 V.
• FILTER, GND, and G100: tied to common return.
• RLOAD: 10 kOhm.

Suggested Experiments

• Increase the input difference by changing VIN+ to 5.20 V.
• Move both inputs up or down together to compare common-mode behavior.
• Add a small capacitor from FILTER to return if transient filtering is being explored.

Featured Component

U1 is the AD626 Difference Amplifier. IN+ and IN- sense the shunt voltage, G100 selects the baseline gain mode, FILTER provides a filter node, GND defines the signal reference, and OUT drives the load.