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cdummie
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I have a problem with understanding this particular circuit given above, just to make it clear, this is the circuit I am talking about (part of this circuit is amplitude control though, but still).

enter image description here

Now, it turns out that, when we are looking for voltage Vo, we do it using superposition principle, so for example, when we are considering only Vcc generator we have:

$$V_o=V_{cc} \frac{R_4+R_5}{R_2+R_3+R_4+R_5}$$

NOTE: I know that this is not the complete expression, V0 will eventually be the same as if we had inverting opamp (in case that R2=R5 and R3=R4)

But, this expression confuses me because it implies that current is the same through all of the resistors R2,...,R4 (R1 is shorted in this case.)

I don't know how is that possible since we have resistor Rf and output of OPamp, shouldn't both of them have a current flowing through, thereby, we would have different currents on resistors R2 and R5 for example.

How come then this expression still happens to be correct in all textbooks, what am I missing?

EDIT: Values of Va and Vb are such that these diodes are off.

I have a problem with understanding this particular circuit given above, just to make it clear, this is the circuit I am talking about (part of this circuit is amplitude control though, but still).

enter image description here

Now, it turns out that, when we are looking for voltage Vo, we do it using superposition principle, so for example, when we are considering only Vcc generator we have:

$$V_o=V_{cc} \frac{R_4+R_5}{R_2+R_3+R_4+R_5}$$

NOTE: I know that this is not the complete expression, V0 will eventually be the same as if we had inverting opamp (in case that R2=R5 and R3=R4)

But, this expression confuses me because it implies that current is the same through all of the resistors R2,...,R4 (R1 is shorted in this case.)

I don't know how is that possible since we have resistor Rf and output of OPamp, shouldn't both of them have a current flowing through, thereby, we would have different currents on resistors R2 and R5 for example.

How come then this expression still happens to be correct in all textbooks, what am I missing?

I have a problem with understanding this particular circuit given above, just to make it clear, this is the circuit I am talking about (part of this circuit is amplitude control though, but still).

enter image description here

Now, it turns out that, when we are looking for voltage Vo, we do it using superposition principle, so for example, when we are considering only Vcc generator we have:

$$V_o=V_{cc} \frac{R_4+R_5}{R_2+R_3+R_4+R_5}$$

NOTE: I know that this is not the complete expression, V0 will eventually be the same as if we had inverting opamp (in case that R2=R5 and R3=R4)

But, this expression confuses me because it implies that current is the same through all of the resistors R2,...,R4 (R1 is shorted in this case.)

I don't know how is that possible since we have resistor Rf and output of OPamp, shouldn't both of them have a current flowing through, thereby, we would have different currents on resistors R2 and R5 for example.

How come then this expression still happens to be correct in all textbooks, what am I missing?

EDIT: Values of Va and Vb are such that these diodes are off.

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JRE
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I have a problem with understanding this particular circuit given above, just to make it clear, this is the circuit iI am talking about (part of this circuit is amplitude control though, but still).

enter image description here

Now, it turns out that, when we are looking for voltage Vo, we do it using superposition principle, so for example, when we are considering only Vcc generator we have:

$$V_o=V_{cc} \frac{R_4+R_5}{R_2+R_3+R_4+R_5}$$

NOTE: iI know that this is not the complete expression, V0 will eventually be the same as if we had inverting opamp (in case that R2=R5 and R3=R4)

butBut, this expression confuses me because it implies that current is the same through all of the resistors R2,...,R4 (R1 is shortenedshorted in this case.) i

I don't know how is that possible since we have resistor Rf and and output of OPamp, shouldn't both of them have a current flowing through, thereby, we would have different currents on resistors R2 and R5 for example. 

How come then this expression still happens to be correct in all textbooks, what am iI missing? Any help appreciated!

I have a problem with understanding this particular circuit given above, just to make it clear, this is the circuit i am talking about (part of this circuit is amplitude control though, but still).

enter image description here

Now, it turns out that, when we are looking for voltage Vo, we do it using superposition principle, so for example, when we are considering only Vcc generator we have:

$$V_o=V_{cc} \frac{R_4+R_5}{R_2+R_3+R_4+R_5}$$

NOTE: i know that this is not the complete expression, V0 will eventually be the same as if we had inverting opamp (in case that R2=R5 and R3=R4)

but, this expression confuses me because it implies that current is the same through all of the resistors R2,...,R4 (R1 is shortened in this case) i don't know how is that possible since we have resistor Rf and and output of OPamp, shouldn't both of them have a current flowing through, thereby, we would have different currents on resistors R2 and R5 for example. How come then this expression still happens to be correct in all textbooks, what am i missing? Any help appreciated!

I have a problem with understanding this particular circuit given above, just to make it clear, this is the circuit I am talking about (part of this circuit is amplitude control though, but still).

enter image description here

Now, it turns out that, when we are looking for voltage Vo, we do it using superposition principle, so for example, when we are considering only Vcc generator we have:

$$V_o=V_{cc} \frac{R_4+R_5}{R_2+R_3+R_4+R_5}$$

NOTE: I know that this is not the complete expression, V0 will eventually be the same as if we had inverting opamp (in case that R2=R5 and R3=R4)

But, this expression confuses me because it implies that current is the same through all of the resistors R2,...,R4 (R1 is shorted in this case.)

I don't know how is that possible since we have resistor Rf and output of OPamp, shouldn't both of them have a current flowing through, thereby, we would have different currents on resistors R2 and R5 for example. 

How come then this expression still happens to be correct in all textbooks, what am I missing?

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cdummie
cdummie
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Amplitude control circuit problem

I have a problem with understanding this particular circuit given above, just to make it clear, this is the circuit i am talking about (part of this circuit is amplitude control though, but still).

enter image description here

Now, it turns out that, when we are looking for voltage Vo, we do it using superposition principle, so for example, when we are considering only Vcc generator we have:

$$V_o=V_{cc} \frac{R_4+R_5}{R_2+R_3+R_4+R_5}$$

NOTE: i know that this is not the complete expression, V0 will eventually be the same as if we had inverting opamp (in case that R2=R5 and R3=R4)

but, this expression confuses me because it implies that current is the same through all of the resistors R2,...,R4 (R1 is shortened in this case) i don't know how is that possible since we have resistor Rf and and output of OPamp, shouldn't both of them have a current flowing through, thereby, we would have different currents on resistors R2 and R5 for example. How come then this expression still happens to be correct in all textbooks, what am i missing? Any help appreciated!