Ok im really struggling to even make a start of this question

For the circuit show find the range of Vi that satisfies Vi=Vo (the top circuit on first image)

So i assumed both diodes are off and solves for D2s cathode voltage and D1s anode voltage

resulting in
D2 ==> V(cath2)>V(anode2) ====> 1.571v>V(anode2) (this is in assumed off status)

D1 ==> V(cath1)>V(anode1) ====> Vcath1>-1.286

But i have no idea how to prove or disprove the result as Vi and Vo are not given
and i don't think i can assume a Voltage of 0v for Vi and Vo with both diodes open because my understanding is not clear if the are voltage inputs of just testing points between the points and earth.

?

 

hi alex,
A couple of hints.
The question is: find the range of Vi that satisfies Vi=Vo
As both diodes are not conducting, assume the range starts at Vi = 0, so Vo =0.
Assume ideal diodes, ie: no forward voltage drop while in current conduction.
E

 

Thanks for your help i believe i found that the range of Vo=Vi to be from -1.286v to 1.571v after that d1 or d2 conducts and the the top left resistor will in turn have a voltage drop/current flow therefor Vi will not equal Vo

Thanks