However, if the input resistors are of different values a scaling summing amplifier is produced which will output a weighted sum of the input signals. If the inputs resistors, R 1, R 2, R 3 etc, are all equal a unity gain inverting adder will be made.
The input impédance of each individuaI channel is thé value of théir respective input résistors, ie, R 1, R 2, R 3 etc.īy putting all of the resistances of the circuit above to the same value R, the op-amp will have a voltage gain of unity and an output voltage equal to the direct sum of all the input voltages as shown.
Likewise, when the summing point is connected to the non-inverting input of the op-amp, it will produce the positive sum of the input voltages. A direct voltage addition can also be obtained when all the resistances are of equal value and R is equal to Rin.
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