Op-amps are widely used in analog electronics. The term Operational Amplifier comes from the original applications of the device in the early 1960s. Op-amps, in conjunction with resistors and capacitors, were used in Analog Computers to perform mathematical operations to solve Differential and Integral Equations. The application of Op-amp has expanded significantly since those early days.

One of the most common applications for an Op-amp is to obtain the algebraic difference or sum of two signals or voltages, such circuits are known as Difference Op-amp and Summing Op-amp.

The Difference Op-amp produces an Output Voltage which is proportional to the algebraic difference between its Input Voltages, Figure 1. The Voltage Gain Gv of the Difference Op-amp can be altered by choosing different resistance values. Figure 2 shows an example of the Output Waveform with two Sine Waves as Inputs of the Difference Op-amp.

Figure 1: The circuit of a Difference Op-Amp

Figure 2: Input and Output Waveforms of the Difference Op-Amp

The relationship between the Input Voltages, V_{IN1} and V_{IN2}, and the Output Voltage V_{OUT1} of the Difference Op-amp is expressed as follows:

The Summing Op-amp is a variation of the Inverting Op-amp configuration, Figure 3. The Summing Op-amp has two Inputs, and its Output Voltage is proportional to the negative algebraic sum of its Input Voltages. Figure 4 shows an example of the Output Waveform with two Sine Waves as Inputs of the Summing Op-amp.

Figure 3: The circuit of a Summing Op-Amp

Figure 4: Input and Output Waveforms of the Summing Op-amp

The relationship between the Input Voltages, V_{IN3} and V_{IN4}, and the Output Voltage V_{OUT2} of the Summing Op-amp is expressed as follows:

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Last Modified Date: 23/9/2024