Can't handle finding currents on the diodes

[Kizteku]

Hello All,

1. Homework Statement
I am confused about applying constant voltage drop model or iteration model . While trying to find the diode currents, results obtained from iteration is not consistent ( I_d1 and I_1k is not equal) so the diode currents .
ALsoIs this convenient to use constant voltage drop because of connecting 0.8v input

Homework Equations

V_d= V_t ln(I_d/I_s)

The Attempt at a Solution

There will be no current on the zener diode since 3v is not satisfied.
The diode is forward biased since 0.8 volt is connected to anode of the diode.
Current on the zener diode is 0.( I_d3 = I_z = 0 )

Hope someone can help
Thanks in advance

 

[berkeman]

Welcome to the PF.

There will be no current on the zener diode since 3v is not satisfied.

Correct. There will be a very small reverse leakage current through the Zener diode, but you can probably ignore it in this case.

If you assume the 0.6V constant forward voltage drop across each of the two forward-biased diodes, you can calculate the current through them by using the leftover voltage drop across each of the series resistors. Can you say what each of those two diode currents would be if there was a constant 0.6V drop across those two diodes?

And if you want to get even more accuracy, you can use the diode equation and the given Is values, but you would also need the diode temperature to correctly apply the diode equation. Do they want you to go that far for this problem? Do they want you to use a typical room temperature for the diode temperature?