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Where is the input supply voltage and what does the circle above Va depict? A current source? What is its value? Also waht are the beta values for the transistor?
I will give you two hints: assume that the current that flows through the bases of both transistors in negligable and it looks like you have a current source above, so the supply voltage beyond doesn't matter...
Now should be able do your homework...
write mesh equations. 3 variable 3 equations..
on solving this u can get currents (a function of transistor Beta) in each branch..
now take the branch with resistors.. calculate voltage across each resistor..
thats all..
looks like a cheap ptat generator to me. where R4/R5 sets the collector current in each device, deltaVbe due to this Ic mismatch is impressed across R2, and Vout = (R1+R2+R3)*Iptat
where Iptat = DeltaVbe/R2
and DeltaVbe = .0259*ln(Ic2/Ic1)
=.0259*ln(R5/R4)
assuming Ic2>Ic1.
Not a bandgap, since there is no diode, but maybe you want a ptat output voltage. Hmm I don't know why you would build this - maybe I should simulate it...
Write mesh equations? wow that's hard - I say just ask the circuit what it is doing, if you are nice it tells you..
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