Level-Shifting Difference Amplifier

Application

This circuit uses the AD629A to subtract two input voltages and produce a single-ended output referred to the REF pins.

Schematic

The differential inputs and supplies are arranged as a source row with a common return rail. REF+ and REF- are tied to that same reference, while OUT drives a load and output probe on the right.

Design Context

VIN+ is 2.10 V and VIN- is 2.00 V, creating a 100 mV differential signal. Grounding both reference pins makes the output table value easy to compare with the input difference.

Expected Behavior

Vout should move with the difference between VIN+ and VIN-. Driving the REF pins away from ground should shift the output baseline without changing the input difference.

Key Values

• VCC / VEE: +15 V and -15 V.
• Inputs: 2.10 V and 2.00 V.
• REF+ and REF-: tied to the common return.
• RLOAD: 10 kOhm.

Suggested Experiments

• Set VIN+ equal to VIN- and confirm the output returns near the reference baseline.
• Raise REF+ and REF- together to explore output level shifting.
• Reverse the input polarity and inspect the sign of Vout.

Featured Component

U1 is the AD629A Difference Amplifier. IN+ and IN- are the subtracting inputs, REF+ and REF- set the output reference behavior, and OUT provides the measured single-ended result.