An inverting amplifier can be constructed as a summing amplifier. The output voltage is a weighted sum of the inverting input signals V1, V2, ……, Vn. Note that each summing coefficient may be independently adjusted by adjusting the corresponding “feed-in” resistor (R1 to Rn). Figure below is an application of inverting configuration and the Vout to Vin transfer function.
An inverting summing amplifier below has three inputs using 100kΩ resistors and a feedback resistor of 50kΩ.
What is VOUT in terms of V1 and V2? If V1 = 2V and V2 = 2V, V3 = 3V what is VOUT ?
VOUT = -50 (V1/100 + V2/100 + V3/100)
VOUT = -50 ((2V+ 2V + 3V )/100 = -3.50V