A summing amplifier, also known as an op-amp summing amplifier or an inverting summing amplifier, is an electronic circuit configuration that combines multiple input voltages and produces an output voltage proportional to the algebraic sum of these inputs. It's commonly used in analog signal processing applications to sum up multiple input signals and generate an output signal that represents their sum.
The summing amplifier is typically built using an operational amplifier (op-amp) as the main active component. An op-amp is a high-gain voltage amplifier with two input terminals (inverting and non-inverting) and one output terminal. In a summing amplifier configuration, the inverting input terminal of the op-amp is used to combine the input signals.
The basic concept of a summing amplifier involves connecting multiple input voltages through individual input resistors to the inverting input terminal of the op-amp. The other end of each input resistor is connected to the respective input signal source. Additionally, there's usually a feedback resistor connected between the op-amp's output and the inverting input terminal. The non-inverting input terminal is usually connected to a reference voltage, like ground, to provide a reference point for the circuit.
The ability of a summing amplifier to combine inputs lies in the linear relationship between the input voltages and the resulting output voltage. The output voltage (Vout) of the summing amplifier can be calculated using the formula:
Vout = - (Rf / Rin1) * Vin1 - (Rf / Rin2) * Vin2 - ... - (Rf / Rinn) * Vinn
Where:
Vout is the output voltage.
Rf is the feedback resistor.
Rin1, Rin2, ..., Rinn are the input resistors corresponding to each input voltage (Vin1, Vin2, ..., Vinn).
Vin1, Vin2, ..., Vinn are the input voltages.
By appropriately choosing the values of the feedback resistor and input resistors, the summing amplifier can be configured to provide various levels of attenuation or amplification for each input signal. It effectively combines the input signals while accounting for their relative strengths and directions, resulting in an output voltage that represents their algebraic sum.