Now compute the voltage developed by R1 (ER1):
Compute the current through R1 (IR1):
Compute the voltage developed by R3 (ER3):
Add this voltage to the voltage at point A to compute the output voltage (Eout):
This was the output desired, so the circuit works as a difference amplifier.
What is the difference between a summing amplifier and an adder circuit?
Can a summing amplifier have more than two inputs?
What is a scaling amplifier?
Refer to figure 3-27 in answering Q31 through Q33.