A summing amplifier is a type of operational amplifier (op-amp) configuration used to combine multiple input voltages into a single output voltage. It's commonly used in analog electronic circuits for various applications such as signal processing, audio mixing, and instrumentation.
The primary function of a summing amplifier is to compute the weighted sum of its input voltages. It takes multiple input voltages, each potentially with its own unique weight or scaling factor, and produces an output voltage that is the algebraic sum of these weighted inputs. Mathematically, the output voltage (
out
V
out
) of a summing amplifier can be expressed as:
out
=
−
(
⋅
1
1
+
⋅
2
2
+
…
+
⋅
)
V
out
=−(R
f
⋅
R
1
V
1
+R
f
⋅
R
2
V
2
+…+R
f
⋅
R
n
V
n
)
Where:
R
f
is the feedback resistor in the summing amplifier circuit.
1
,
2
,
…
,
V
1
,V
2
,…,V
n
are the input voltages.
1
,
2
,
…
,
R
1
,R
2
,…,R
n
are the input resistors associated with each input voltage.
The negative sign in the equation is a result of the inverting nature of the op-amp configuration typically used in a summing amplifier.
By appropriately choosing the values of the input resistors and feedback resistor, along with their relationships to the input voltages, you can control the scaling and weighting of the input voltages to generate the desired output voltage. This is particularly useful in applications where you need to combine signals with different amplitudes and contributions, such as mixing audio signals or adding various sensor inputs.
Summing amplifiers are a fundamental building block in analog circuit design, and their ability to combine input voltages while allowing for precise control over the contributions of each input makes them essential in many engineering and electronic applications.