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Which R2? Post the actual schematic..
Ok, so lets look at the first stage. If the voltage on the output of the opamp is 1V, then the current through R2 will be 100uA. Where does this current come from? It is going from the positive supply rail, through the current mirror, into the positive supply pin of the opamp and through the output out into R2.
The opamp needs some supply current to work, lets say this current is 1mA. This current will flow through both the upper and the lower mirror, so the current through the top mirror should be 1mA + 100uA, and the current through the bottom mirror should be 1mA. The difference in those two currents needs to flow through R1 because those two ends of the mirrors are connected together and you cant have 1.1mA and 1mA flowing through at the same time, so there will be 100uA flowing through R1, which will produce 0.1V at the point R1 connects to those two mirros.
Now, the second opamp needs to provide -100uA into R3 to keep the input of the opamp at 0V. 100uA*R3 is 1V, so I was wrong in the last post. The frist opamp has gain of 1, the current mirror produces gain of 0.1 and the third opamp has gain of -10, resulting in overall gain of -1.
I still dont see how you came up with such a circuit, or why are you trying to actually use it. I don´t see any benefit over using just the opamps, this circuit is just much worse in real life.
That is because whatever current is flowing through the output needs to come from the supply rails.I really appreciate ur help. I don't understand one part, why should the current of top mirror be 1mA+100uA and the current of bottom mirror must be 1 mA?
No, I meant the other side of R1.One more thing, You said "so there will be 100uA flowing through R1, which will produce 0.1V at the point R1 connects to those two mirros." You mean 0.1v will be produced at the connection of R1 and R3, right?
This circuit has been given to me. I should analyze it and assemble on breadboard to see what's going on. this circuit is one part of the main circuit but I'm told I have to
analyze this part first. I try to upload the file of whole circuit very soon. it's not clear to me why is this current mirror used! I have one question when we want to get gain of first stage the output voltage is end of the resistor (R3)? it seems strange to me gain of first stage is R1/R2.
Yes, negative supply goes to V-, and the positive to V+.