This document describes a summing amplifier circuit using an operational amplifier (op-amp). The summing amplifier allows multiple input signals to be added together at the output. It discusses an inverting summing amplifier configuration with three input voltages V1, V2 and V3. The circuit produces an output voltage proportional to the algebraic sum of the three input voltages, effectively adding them, because each input sees its own resistor and they are isolated by the op-amp's virtual earth. Scaling can also be achieved if the input resistors are unequal.

1. Sub:-BASIC ELECTRONICS
Topic:-Summing Amplifier using OP-AMP
Made by:-ASHISH MISHRA (150140111055)

2. Summing Amplifier
• It is possible to apply more than one input single to an inverting
amplifier. This circuit will then add all these input signals to
produce at the output.
• Such a circuit will then be called an adder or a summing
amplifier.

3. Types
Non-invertingInverting adder

4.  The inverting summing amplifier configuration with three inputs V1, V2, and
V3
 Depending on the relation between the feedback resistor RF and the three
input resistor R1, R2 and R3 we can use the same circuit shown in figure.
 V1, V2 and V3 are measured with respect to ground. Rf is the feedback
resistor connected between the output terminal and the inverting input
terminal of OP-AMP. The non-inverting input terminal is connected is ground.

7. • We now have an operational amplifier circuit that will
amplify each individual input voltage and produce an
output voltage signal that is proportional to the algebraic
“SUM” of the three individual input voltages V1, V2 and V3.
We can also add more inputs if required as each individual
input “see’s” their respective resistance, Rin as the only
input impedance.

8. • This is because the input signals are effectively
isolated from each other by the “virtual earth” node at
the inverting input of the op-amp. A direct voltage
addition can also be obtained when all the resistances
are of equal value and Rƒ is equal to Rin.
• A Scaling Summing Amplifier can be made if the
individual input resistors are “NOT” equal. Then the
equation would have to be modified to: