AKA Adder
Vo = -(V1 + V2)(R1/R2)
The 2 most left resistors represent R2. The resistor on top represents R1.
If R1 and R2 are equal, the amplifier just sums up the voltages of the voltage sources(and inverts the sum ofcourse). Play around with the resistors to have some fun(I recommend the top resistor(R1))
