Operational Amplifier Fundamentals Unit 6 – The Noninverting Summing Amplifier
UNIT 6 – THE NONINVERTING SUMMING AMPLIFIER
UNIT OBJECTIVE
At the completion of this unit, you will be able to describe the operation of a noninverting
summing amplifier.
UNIT FUNDAMENTALS
In a noninverting summing amplifier, the (-) terminal acts as the op amp summing junction.
The (+) terminal acts as the summing point (VA) of the individual circuit input voltages.
VA is multiplied by the circuit gain factor [1 + (RF/R1)] to generate the output voltage (VO).
Due to the high impedance of U1, VA is determined by the superposition theorem. However, if
R1 and R2 are equal in value, VA = (V1 + V2)/2.
NOTE: V1, V2, and VA are measured with respect to circuit common.
U1 is not zero based because the (+) input terminal is not returned to circuit common. VA can be
greater than 0V (positive) or less than 0V (negative).