A summing amplifier, also known as an adder amplifier, is a type of operational amplifier (op-amp) circuit configuration used to combine multiple input signals into a single output signal. It's commonly used in analog electronic circuits to perform arithmetic operations such as addition or subtraction of voltage signals.
The basic concept behind a summing amplifier is to create a weighted sum of the input voltages, where each input voltage is multiplied by a specific constant (gain factor) before being added together. The output voltage of the summing amplifier is the result of this weighted sum.
The general circuit diagram of a summing amplifier consists of an operational amplifier with multiple input resistors connected to the inverting (-) input terminal. Each input voltage is connected through a resistor to the inverting input, and the other ends of the resistors are usually tied together at a common node (sometimes with a feedback resistor for stability). The non-inverting (+) input terminal of the op-amp is usually grounded.
The ability of a summing amplifier to combine input signals is determined by the values of the input resistors and their corresponding gain factors. The gain of each input signal can be adjusted by choosing the appropriate resistor values. The output voltage of the summing amplifier can be calculated using the following formula:
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 of the summing amplifier.
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.
V_1, V_2, ..., V_n are the input voltages.
By appropriately selecting the resistor values, you can control the weights of the input voltages in the final sum, allowing you to combine different signals in desired proportions. This makes the summing amplifier a versatile component in various applications such as audio mixing, signal processing, and instrumentation, where you need to combine and manipulate multiple input signals to obtain a specific output response.