1. The problem statement, all variables and given/known data 2. Relevant equations r_d= V_T/I_D, V_T=25mV 3. The attempt at a solution i alreayd find the operation of diodes, D1 off and D2 on (2nd circuit). the current through this diode i also calculate as 34mA, also r_d=0.7353 ohm. I am having trouble using incremental model, in my book it gives voltage divider like V(r_d/(r_d+R)) where V is ripple in voltage (+1 here) and R is I guess the eq. resistance. except I don't think I can voltage divider here, I try to change the V source to 3.7 and 5.7V (+1) and I get the diode curent change by 1mV each time.. but not sure how to prove this. Using node voltage I find V at node is -20V, the diode current is (4.7+1+20)/1k + (20)/1.93k this also give change in diode current +1mA for +1V of the 10V source, but is this the right way to do it?