GATE EC 2025 Set 1 — Question 63
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Electronic Devices → P-N Junction & Diodes → Diode Equation & Resistance
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Question
An ideal p-n junction germanium diode has a reverse saturation current of at .
The voltage (in Volts, rounded off to two decimal places) to be applied across the junction to get a forward bias current of at is __________.
(Consider the Boltzmann constant and the charge of an electron .)
The voltage (in Volts, rounded off to two decimal places) to be applied across the junction to get a forward bias current of at is __________.
(Consider the Boltzmann constant and the charge of an electron .)
Correct answer
0.23 to 0.24
Solution
The diode current equation for a p-n junction is given by:
where:
is the forward bias current =
is the reverse saturation current =
is the applied voltage across the junction (to be found)
is the ideality factor. For germanium, .
is the thermal voltage, given by Given:
Boltzmann constant
Charge of an electron
Temperature First, calculate the thermal voltage :
Now, substitute the values into the diode current equation:
Divide both sides by :
Add 1 to both sides:
Take the natural logarithm of both sides:
Calculate :
V V = 9.2104 \times 0.025875 V \approx 0.23846 V0.24\boxed{0.24}$
where:
is the forward bias current =
is the reverse saturation current =
is the applied voltage across the junction (to be found)
is the ideality factor. For germanium, .
is the thermal voltage, given by Given:
Boltzmann constant
Charge of an electron
Temperature First, calculate the thermal voltage :
Now, substitute the values into the diode current equation:
Divide both sides by :
Add 1 to both sides:
Take the natural logarithm of both sides:
Calculate :
V V = 9.2104 \times 0.025875 V \approx 0.23846 V0.24\boxed{0.24}$
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