Name of the Experiments: Demonstration on Closed-loop Summing Amplifier.

Objective:

This experiment is intended to observe the operation of Op-Amp IC as Summing Amplifier.

Apparatus:

1. Digital Multimeter

2. Oscilloscope

3. Trainer board.

4. Connecting wires

5. Op-amp IC(LM351/ μA741)

6. Resistors

7. Power supply

Theory: Summing Amplifier

A Summing amplifier is in fact an operational amplifier( op-amp ) configured in a specific manner. An ideal op-amp has characteristics like infinite input impedance, infinite gain and zero output impedance. Based on its unique properties, an op-amp can be configured for various function, including a summing amplifier Also known as the adder the Summing amplifier produces a voltage output that is equivalent to an amplified sun of two or more input voltage usually, a Summing amplifier is infect an inverting amplifier, which means the output voltage has a negative value when measured to ground. The summing amplifier can be build using two op-amp configurations Inverting or Non-inverting

Inverting Configuration:

Figure 01: Inverting three input summing amplifier

Figure 01, shows the inverting configuration with three inputs va, vb, vc. Since Ri and A of the op-amp are ideally infinity,

Non-inverting amplifier:

Figure 2: Non-inverting three input summing amplifier

If the voltage sources and the resistors are connected to the non-inverting terminal as shown in figure 2, the circuit can be used as summing amplifier. By applying Super Position theorem at the input section we get,