GATE 2024 EE – Question 60
In the given circuit, the diodes are ideal. The current $I$ through the diode D1 in milliamperes is ___________ (rounded off to two decimal places).
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Correct answer: 1.66 to 1.68
Explanation
Assume both diodes conduct. D1 (ideal) holds node B at 3 V. Let node A be the junction of the two 1 kΩ resistors on the left. D2 conducts from A to B through the 1 kΩ resistor: $I_{D2}=\dfrac{V_A-3}{1\text{ k}}$. KCL at A: $\dfrac{10-V_A}{1}=\dfrac{V_A}{1}+\dfrac{V_A-3}{1}$ (in mA, kΩ), so $V_A=\dfrac{13}3=4.33$ V and $I_{D2}=1.33$ mA. At B the 1 kΩ to ground draws 3 mA, so $I=3-1.33=1.67$ mA $>0$, and $I_{D2}>0$: both diodes indeed conduct.