Hello guys since yesterday I'm trying to resolve this probleme...I need to calculat V' and V" for both cases when Ve > 0 and Ve <0 and then Vs.

Voltage of diode is 0.6V.

At first I supposed that D2 is blocked and D1 is not blocked, but then I stuck on how to calculate V' and V" because of the current.
if anyone can help me I will be thankfull.
Have a good day.

 

hi k2913,
Cleaned up your circuit image.
E

 

hi k2913,
Cleaned up your circuit image.
E
View attachment 143734

Thanks!

 

Hello guys since yesterday I'm trying to resolve this probleme...I need to calculat V' and V" for both cases when Ve > 0 and Ve <0 and then Vs.

Voltage of diode is 0.6V.

At first I supposed that D2 is blocked and D1 is not blocked, but then I stuck on how to calculate V' and V" because of the current.
if anyone can help me I will be thankfull.
Have a good day.

Hi,

You have to vary Ve and figure out when D1 is conducting and when D2 is conducting. It is not a matter of assuming that really, it is a matter of assuming that the input starts from zero and goes up to some value, then down through zero and then negative. If you calculate the output of the first op amp you can easily decide which diode is 'on' at that time and then calculate the very output.

Just for example, say you have +0.1v input. What is the output voltage of the first op amp, then what is the voltage across the two diodes, then which one is 'on'.
Also keep in mind that the gain of the op amp in open loop could be 10000 or even 100000, so even a small input to one terminal if the other is zero will result in a large output voltage. That means that even with a small input voltage one of the diodes will conduct.
Once you figure out which one conducts, you can then apply the feedback and see how that limits the output.

This is just a little tricky because the way the output of an op amp changes open loop.
The overall operation however is simple, once you figure out how the diodes conduct when when they conduct.