Operational amplifier as summer
An operational amplifier as a summer (Op-Amp as Summing Amplifier) can also perform additions. The summing amplifier is based on the principle of the inverting amplifier, with the difference that the input current is generated by two or more different input voltages. The input currents add up and are amplified as usual:
Op-Amp as Summing Amplifier - Operational amplifier as summer
Since the inputs of the operational amplifier are at the virtual zero point and the differential voltage between the inputs is zero, the following applies: Ve- = - VOUT
Since the input resistances of the operational amplifier are, as we know, very large, the input currents are negligible. Thus applies: If = IIN1 + IIN2+ IIN3 + …
With Vf = Rf * If and Vf = - VOUT you get:
Applications operational amplifier as a summer:
- Adder
- Generation of mixed voltages
- Digital/analog converter