Help Understanding Circuit Requirements for Conducting Diode

[zsolt2]

Hi all. I need some help with the circuit attached.
For the diode to conduct, at point X the voltage must be 0.6V minimum. There is an equation to find the minimum required voltage input, Vin to give 0.6V at X. What I don't understand is the right hand side of the equation; why is it:
(0.6-(-10))/2.2x10^3
why subtract 10 out of 0.6 and not the other way around? I understand that ((Vin-0.6)/10^3) is the current developed in the 1k resistor and (0.6-(-10))/2.2x10^3 is the current in the 2.2k resistor. So the 0.6V is comming from the 1k towards the diode and the 2.2k resistor where it meets with -10V. Shouldn't the 0.6 be subtracted from the -10V then?
what I thought is that it supposed to be:
((Vin-0.6)/10^3) + (-10-0.6)/2.2x10^3
((Vin-0.6)/10^3) + -10.6/2.2x10^3
((Vin-0.6)/10^3) - 10.6/2.2x10^3
((Vin-0.6)/10^3) = 10.6/2.2x10^3

It will give the same result as the equation provided. Can you explain the circuit a bit and that where did I go wrong?
Thank you!

 

[jim hardy]

What I don't understand is the right hand side of the equation; why is it:
(0.6-(-10))/2.2x10^3

Always go back to your basics
draw in currents and polarities then write KVL

 

[jim hardy]

What I don't understand is the right hand side of the equation; why is it:
(0.6-(-10))/2.2x10^3

looks to me like an addition not a subtraction
and i think that's what you said

Shouldn't the 0.6 be subtracted from the -10V then?

Your intuition was right
form the habit of confirming your intuition with KVL

old jim

 

[zsolt2]

Thank you Jim!