Seen from the attached pictuire.
Based on bandgap requirement, Ic1=Ic2.
Because Ic2 and Ic3 are in series--> Ic2=Ic3
Because of size ratio n, Ic4=n*Ic3
So Ic4=n*Ic1
But Ic4 and Ic1 are in series, Ic4 should be equal to Ic1. It conflicts with Ic4=n*Ic1.
Where is my error in this above deduction? I'm puzzled about it.
As Aparna Sathya Murthy points out, your notation is poorly specified and confusing. Are IC3, IC4 collector currents of Q3, Q4 or emitter currents as shown in your diagram?
What are IS, IS1, IS2, IS3, IS4, V? These are not labelled on the diagram. Is there any external current into the connection to Q4 collector and the resistor attached to Q1 collector?.
Why do you assume IC1 = IC2 ?
In your circuit diagram, there is no bias current to the bases of either of the two PNP bipolar transistors, Q3 or Q4, so collector currents from both these transistors will be at leakage levels and very small.
For a PNP current mirror, you should connect bases Q3 and Q4 to collectors of Q4 and Q2. In this case VBE1 = VBE2 + RE2 IE2, where RE2 is the emitter resistor and IE2 the emitter current of Q2.
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