Summing amplifier using OPAM

Summing amplifier using OPAM

In this article I will throw some light on Summing amplifier using OPAM. An OPAM i.e. Operational Amplifier can be used to perform mathematical operations such as addition, subtraction, differential amplifier, integrator, etc. In this article we will see how OPAM can be used as addition or summing amplifier.

Here, as we have used the OPAM in close loop configuration, we will assume that there is negligible voltage difference between inverting input and non inverting input. So for calculations Voltage at PIN2 = 0.

Here I1, I2, I3 are three inputs, with resistance R1, R2, R3. Current in these three wires will be:

I1 = V1 /R1

I2 = V2/R2

I3 = V3/R3

This current will pass through feedback resistance.

I fb = – (I1 + I2 + I3)

Vo/ Rf = -(V1/R1 + V2/R2 + V3/R3)

here we have used R1 = R2 = R3 = Rf

Hence

Vo = -(V1 + V2 + V3)

We get our output as sum of inputs that is why this configuration is known as summing amplifier. By choosing different set of R1, R2, R3 and Rf we can also make this configuration change into weighted amplifier.

For example if we choose

Rfb/ R1 = 2

Rfb/R2 = 3

Rfb/R3 = 1

Therefore, output will be

Vo = -(2V1 + 3V2 + V3)

In this way we can use our OPAM in many mathematical calculations. Watch this video to see it working on Proteus 7.7.