Inverting Summing Amplifier

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 changing the corresponding “feed-in” resistor (R1 to Rn). The included figure is an application of inverting configuration and the Vout to Vin transfer function.



An inverting summing amplifier below has three inputs using 100 kΩ resistors and a feedback resistor of 50 kΩ.
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

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