A summing amplifier, also known as an op-amp summing amplifier, is an electronic circuit configuration that combines multiple input signals to produce an output signal that is proportional to the sum of its inputs. This type of circuit is commonly built using operational amplifiers (op-amps), which are versatile electronic devices used for amplification, signal processing, and various other applications.
The basic idea behind a summing amplifier is to use the properties of an op-amp to create a weighted sum of the input voltages. The circuit typically consists of an op-amp and multiple input resistors connected to its inverting (-) input terminal. Each input signal is connected through its corresponding resistor to the inverting input terminal. The non-inverting (+) input terminal of the op-amp is usually connected to a reference voltage (such as ground) to maintain the desired behavior of the circuit.
The formula for calculating the output voltage of a summing amplifier is as follows:
V_out = - (Rf / R1) * V1 - (Rf / R2) * V2 - ... - (Rf / Rn) * Vn
Where:
V_out is the output voltage.
Rf is the feedback resistor connected between the output and inverting input of the op-amp.
R1, R2, ..., Rn are the input resistors connected to the inverting input of the op-amp for each input signal V1, V2, ..., Vn.
V1, V2, ..., Vn are the input voltages.
Each input voltage is multiplied by a weighting factor determined by the ratio of the feedback resistor to the corresponding input resistor. The negative sign in the formula arises from the inverting configuration of the op-amp, which means that the output is phase-inverted with respect to the input.
By adjusting the values of the input resistors and the feedback resistor, you can control the weights and the scaling of the input signals in the output. This allows you to create various linear combinations of input signals, making the summing amplifier a useful tool in applications such as audio mixing, signal processing, and mathematical operations.