So, then Mesh analysis? I'll end up with 4 Loops? But how can I determine which one is on and which one is off?!

If you build the circuit then measure the voltages...Draw out the current would flow.. D3 can't be on cause it has 0v and the positive side of the diode facing the source voltage ... D2 has less voltage than the 10v and is closer to the -5v which with the voltage drop and resistors ,the output should be 0v or pretty close .. D1 has the highest voltage but will flow even though the voltage drop with the diodes and resistors ...Don't quote me here cause I could be completely wrong and please correct me if I am .. I am still learning and this is how I look at the circuit..

 

So, then Mesh analysis? I'll end up with 4 Loops? But how can I determine which one is on and which one is off?!

No need for mesh analysis, just calculate the voltages at the resistor nodes wrt 0V without the diodes. You can then determine whether each diode is forward-biased or not. A forward-biased diode will have an effect on the node voltages so this has to be taken into account.

The diode drops should have been stated as this affects the result and is never zero for a real diode.

 

0V

NO.

You never will understand the answer because the answer is wrong. Not incomplete, not misunderstood, not inaccurate; just plain wrong.

There is no diode on this planet that has Vf = 0. If that is a condition of the question, quit wasting our time. This is an electrical engineering forum on Earth, not fantasyland on Mars.

ak

 

Well, you got it, but how?!

I used the voltage drop across the entire load to estimate current, then calculated the voltage drop into each node and assumed a forward bias drop of 0.7 as the diode's conduction point (although conduction can start at 0.4v)

 

OP starts asking for help and ends explaining who is right or wrong....!

 

OP starts asking for help and ends explaining who is right or wrong....!

I know but doesn't know why who is right or wrong. I just ran the circuit on my phone and posted the results as per the request..

 

OP starts asking for help and ends explaining who is right or wrong....!

I disagree, the OP did not do any explaining at all.

 

Hi,
In this pic I'm only sure about D1 which is ON and for D2 and D3 I'm not really sure about them! So, please help me out how can I determine whether if they are on or off and how?
thanks in advance.

View attachment 90910

Remove D2 and D3 so that you have a simple series circuit that from the +10V on the left through D1 and then the three resistors to the -5V on the right.
Figure out the voltages at the junctions of the resistors. Are those voltages such that both D2 and D3 would be off? If so, then you are done.

If one or both would be on, then insert them and determine the voltages at the junctions of the resistors and then determine the currents to verify that the diodes are in the state that you assumed. If they are not, then you should be able to determine what the correct state most likely is.

Another way would be to assume that all three diodes are on and determine their currents. Any that would require current flowing backward through it must be off. So turn that diode off and repeat.

A next step in this puzzle would be to determine the state of D1,D2,D3 as a function of the (assumed constant) value used for Vf, starting from Vf=0V (ideal diode model) to Vf=15V (the point above which all three diodes will be OFF).