A summing amplifier is an electronic circuit used to combine multiple input voltages and produce a single output voltage that is the algebraic sum of all the input voltages. It is also known as an op-amp (operational amplifier) summer or an inverting summer. The primary function of a summing amplifier is to sum the weighted input voltages to create a combined output voltage.
The basic configuration of a summing amplifier consists of an operational amplifier and several input resistors connected to its inverting (-) input terminal. Each input voltage is applied through a separate resistor to the inverting input. The non-inverting (+) input terminal is usually connected to a reference voltage or ground.
The formula for calculating the output voltage of a summing amplifier is as follows:
V_out = - (R_f / R_1) * V_1 - (R_f / R_2) * V_2 - ... - (R_f / R_n) * V_n
Where:
V_out is the output voltage.
R_f is the feedback resistor (connected between the output and the inverting input of the op-amp).
R_1, R_2, ..., R_n are the input resistors connected to each input voltage V_1, V_2, ..., V_n.
The negative sign in the formula indicates that the output voltage is an inverted representation of the sum of the input voltages. The magnitude of each input voltage's contribution to the output is determined by the ratio of the feedback resistor to the corresponding input resistor.
The ability to combine input voltages and create a weighted sum makes the summing amplifier useful in various applications, such as analog signal processing, audio mixing, and instrumentation. By adjusting the values of the input resistors, different weightings can be applied to each input, enabling fine-tuning of the output signal. This flexibility allows engineers to design circuits that can accurately add and scale different analog signals as needed in complex electronic systems.