A summing amplifier is a type of operational amplifier (op-amp) circuit configuration that is designed to combine multiple input voltages and produce an output voltage that is proportional to the algebraic sum of its input voltages. In other words, it adds or sums the individual input voltages together. This type of circuit is commonly used in analog signal processing and analog computation applications.
The basic concept behind a summing amplifier is to use the properties of an op-amp to create a weighted sum of its input voltages. The op-amp's high input impedance and low output impedance make it well-suited for this purpose.
The general circuit diagram of a summing amplifier consists of an op-amp with multiple input resistors connected to its inverting input terminal (often referred to as the "virtual ground") and a feedback resistor connected from the output to the inverting input. The input voltages are applied through the input resistors, and the feedback resistor determines the gain of the circuit.
The formula for the output voltage of a summing amplifier is:
Vout = - (Rf / R1) * Vin1 - (Rf / R2) * Vin2 - ... - (Rf / Rn) * Vinn
Where:
Vout is the output voltage.
Rf is the feedback resistor.
R1, R2, ..., Rn are the input resistors connected to each input voltage Vin1, Vin2, ..., Vinn.
Each input voltage is multiplied by the ratio of the feedback resistor to the corresponding input resistor. This allows you to control the contribution of each input voltage to the final output.
The summing amplifier can be used for various applications, such as audio mixers, signal conditioning, voltage summing, and analog computation. By appropriately choosing the resistor values, you can adjust the amplification and polarity of each input voltage in the sum. Keep in mind that practical considerations, such as the op-amp's voltage supply range and bandwidth, need to be taken into account when designing and using summing amplifier circuits.