In the circuit shown below voltage Vin is 3V and VB is 1V. The resistor R1 and R2 are 1K. Assume both diodes are identical. Forward bias resistance is 10Ω. Cut-in voltage of diode is 0.7V. The voltage Vout is __________

In the circuit shown below voltage Vin is 3V and VB is 1V. The resistor R1 and R2 are 1K. Assume both diodes are identical. Forward bias resistance is 10Ω. Cut-in voltage of diode is 0.7V. The voltage Vout is __________ Correct Answer 1.314V

Since D1 and D2 are forward biased we can replace them with their equivalent diagram. Assume I be the current through the circuit. By kirchoff’s voltage rule, Vout = -VD+IRD+IR2 ————(1) Current through R1 (Vin-Vout)/1k = (3-Vout)/1k Current through diode is (Vin-Vout-VD-VB)/RD = (0.3-Vout)/10 Total current I = (3-Vout)/1000+(1.3-Vout)/10 = 1.330-1.010Vout Substitute this in eq(1) That is, Vout = -0.7 + 1010(1.33-1.01Vout) 1021Vout = 1342. Therefore, Vout = 1.314V.