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Find current I if voltage V = 5V, VB = 2V, R1 & R2 = 2K. Use ideal diode model assumption.(a) 1.5mA(b) 1.375mA(c) 2mA(d) 3mAI got this question at a job interview.Origin of the question is Ideal Diode Model topic in portion Diode Circuit of Analog Circuits

Answer»

The CORRECT OPTION is (d) 3mA

Best explanation: In IDEAL diode MODEL the diode is considered as a perfect CONDUCTOR in forward bias and perfect insulator in reverse bias. That is voltage drop at forward bias is zero and current through the diode at reverse bias is zero.

The diode is forward biased and can be considered as a short circuit.

 So voltage across R1 is V-VB.

 That is 3V. Therefore, current through R1 = 3V/2k = 1.5mA.

Current through R2 = 3/2K = 1.5mA.

Therefore, total current I = 1.5+1.5 = 3mA.


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