Skip to Content

Inverting Summing Amplifier

Last modified by Microchip on 2023/11/09 08:59

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 1 is an application of inverting configuration and the Vout to Vin transfer function.

Application of inverting configuration and the Vout to Vin transfer function

Figure 1

summing amp transfer function

Figure 2

Example

Figure 3 is an inverting summing amplifier with 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 ?

Inverting summing amplifier example

Figure 3

Answer

VOUT = -50 (V1/100 + V2/100 + V3/100)

VOUT = -50 ((2V+ 2V + 3V )/100 = -3.50V