# Signal and system summing opamp math calculation support argument

#### majdi

Joined Jun 22, 2011
23
Hello and good day all, i need advice on this question. At least keyword or url so i can study more. For electronic calculation i successfully calculate gain, -vout and else. But this type i not really understand when input in x1(t), x2(t) the vout in y(t). #### ericgibbs

Joined Jan 29, 2010
10,518
hi m,

Mathematical functions are usually expressed as: y =f(x) .
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#### ericgibbs

Joined Jan 29, 2010
10,518
As its a Inverting Summing amp, its purpose is to add together the x1(t) and x2(t) signals together, and give the Sum as y(t),, the same as you would do adding two numbers,
Consider what effect the 'Inverting' within the amp will do to the polarity of y(t).

So your first, y(t)= x1(t) + x2(t) equation is correct, but include the inversion.

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#### majdi

Joined Jun 22, 2011
23
i). Time-varying or Time-invariant

y1(t-t0) -> corresponding to x2(t)
x2(t) -> x1(t-t0)
x2(t) -> coorresponding to y2(t)
y1(t-t0) = y2(t) Is not true. Which mean this is Time-Varying System.

ii). Linear or Nonlinear
-y(t) = x1(t)+x2(t)
The system is in linear system because the condition is in additive or superposition property.

iii). Instantaneous or Dynamic
The system is Dynamic System, this is because the output y(t) response at any instant t depend not only on the present value of input, but also on the past values of the input which is the value before t.

iv). Causal or Non-causal

This is Causal System because -y(t) = x1(t)+x2(t), which mean y(t) to the input does not depend on future values of that input, x1(t-t0) and x2(t-t0) but only on the x1(t) and x2(t) present and or past values of the input, x1(t-t0) and x2(t-t0).

v). Open-loop or Close-Loop

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#### ericgibbs

Joined Jan 29, 2010
10,518
v). Open-loop or Close-Loop