Opamp Voltages: Finding Output Voltage with Inverting and Non-Inverting Amps

[PhysKid45]

Homework Statement

There are unknown values for input voltage, but we know it is sinusoidal. There is an inverting amp connected in parallel with a non inverting amp. The goal is to find the output voltage.

I have three questions.
1: if the problem states that "power rails for both opamps are in the same range" what does that mean, what is a power rail?
2: Is it safe to assume Vin to each amp are equivalent bc the voltage would be the same through the separate parallel branches.
3: Should the output voltage of each opamp add to the total voltage, or should they be equivalent to each other (and the total) because it is all the same loop?

Homework Equations

Inverting amp: vout/vin = -r2/r1
non inverting amp: vout/vin = 1+(r2/r1)
kirchoff's laws

The Attempt at a Solution

I do not need/want help with a full solution. Simply a few questions about summing amplifier voltages.

 

[Merlin3189]

There are unknown values for input voltage, but we know it is sinusoidal...
I have three questions.
1: if the problem states that "power rails for both opamps are in the same range" what does that mean, what is a power rail?
2: Is it safe to assume Vin to each amp are equivalent bc the voltage would be the same through the separate parallel branches.
3: Should the output voltage of each opamp add to the total voltage, or should they be equivalent to each other (and the total) because it is all the same loop?
View attachment 213589
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I do not need/want help with a full solution. Simply a few questions about summing amplifier voltages.

1. All op amps need a DC power supply, but it is largely irrelevant to the basic function of the circuit, so not shown. It will affect the maximum size of output voltage achievable and the range of permissible inputs, since all pins must remain within these bounds. That is a practical issue in the choice of which IC to use and what power supply to use, once you have designed your functional circuit. Here I think they are saying, don't concern yourself with that.
2 Yes. The signal is shown as an ideal voltage source, so assume it will maintain the signal voltage at its output for any reasonable current drain. In any case, we assume for now the op amp is ideal and no current flows into (nor out of) the inputs.
3 Again assume ideal op amps. The output is a low impedance voltage source which will not be affected by reasonable loads. So you can calculate v1 and v2 ignoring the load.

Having achieved an ideal design, one would have to think about reality in order to build a working circuit. Then you would look at what chips and power arrangements you would need to cope with the size of signal you were handling, at how any deviation from ideal components affected the required operation and at the properties of your actual voltage source. But that is for much later! For many small signal, low frequency situations you just use any old op amp and your bench supply and it is good enough.

 

[rude man]

Homework Statement

3: Should the output voltage of each opamp add to the total voltage, or should they be equivalent to each other (and the total) because it is all the same loop?

Compute v1 and v2 separately, then V = v1 - v2.