Weighted Summer Operational Amplifier Circuit

Weighted Summer Circuit

In this video, the instructor explains the weighted summer circuit using an operational amplifier. The circuit is used to show voltages and involves adding a few resistors on the negative side of the operational amplifier.

Operational Amplifier Circuit

• The circuit consists of an operational amplifier with a feedback resistor from the output going back into the negative input.

• On the negative side, three resistors are connected at a junction point where voltages are inputted.

• Due to virtual ground assumption, both inputs are at zero volts. A current flows into one resistor (R), while i1, i2, and i3 flow into each of the three resistors respectively.

Calculating Output Voltage

• The sum of i1, i2, and i3 equals I. Using Ohm's law we can calculate that I1 = V1/R1, I2 = V2/R2 and I3 = V3/R3.

• To find Vnaught (V0), we use Kirchhoff's voltage law which states that V0 is equal to 0 minus IR where I is equal to I1 + I2 +I3.

• We can rewrite this equation as -RV1/R1 - RV2/R2 - RV3/R3 which shows that Vnaught is equal to the negative sum of weighted voltages.

Conclusion

• The output voltage (Vnaught) in a weighted summer circuit is equal to the negative sum of weighted voltages.