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Find current I if V = 5V and -5V when VB = 2V, R1 = 2KΩ, R2 = 4KΩ and the diode is ideal.(a) 0A and 1.3mA(b) 1.231mA and 0.33mA(c) 3.25mA and 0A(d) 1.58mA and 0AThis question was addressed to me in an interview for job.Enquiry is from Ideal Diode Model topic in portion Diode Circuit of Analog Circuits

Answer»

The correct answer is (c) 3.25mA and 0A

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.

When V=5V, the diode is forward biased and can be considered as a SHORT circuit.

Current through resistor R1 = V/2k = 2.5mA.

Current through resistor R2 = (V – VB)/4k = 0.75mA.

So total current is3.25mA.

At V = -5V, diode is reverse bias So the current is zero.


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