5. The diodes in the circuit below have a turn-on voltage of 0.7 V. Determine th

Question

5. The diodes in the circuit below have a turn-on voltage of 0.7 V. Determine the state of the diodes and the value of Vx and i. VS R1 R2 R3 R4 15V 10 k(Ohm) 5 k(Ohm) 5 k(Ohm) 10 k(Ohm) IMAGE URL: http://www.johnloomis.org/egr203/asgn/asgn13/fig4.jpg

Explanation / Answer

Let us assume both D1 and D2 are in forward bias Nodal analysis the voltage at the end of R2 will be Vx+.7 for it to be forward bias and the end of R3 is Vx+.7 => Vs-Vx-.7/R3 +(Vs-Vx-.7)/R1 =Vx/R4 +(Vx+.7)/R2 3*(14.3-Vx)/10 =Vx/10+Vx+.7/5 =>42.6-3Vx=Vx+2Vx+1.4 =>6Vx = 41.2 =>Vx= 6.87 V for i i= Vs-(Vx+.7)/R1 - (Vx+.7)/R2 = 14.3-6.87/10 - (6.87+.7)/5 = .743 - 1.514 = -ve which is not possible as D2 is in forward bias so our assumption is wrong now assume that D1 is reverse and D2 is forward => now nodal analysis we get Vs-(Vx+.7)/R1 = (Vx+.7)/R2+Vx/R4 =>14.3-Vx/10 = Vx+.7/5 + Vx/10 =>14.3-Vx=2Vx+1.4+Vx =>4Vx=12.9 =>Vx=3.225 V i=Vx/R4 = 3.225/10 = .3225 mA

Related Questions

Navigate

• Browse (All)
• Browse 5
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.