# GATE Questions & Answers of BJT

## What is the Weightage of BJT in GATE Exam?

Total 9 Questions have been asked from BJT topic of Electronic Devices subject in previous GATE papers. Average marks 1.78.

A MOSFET in saturation has a drain current of 1 mA for VDS =0.5 V. If the channel length modulation coefficient is 0.05 V-1, the output resistance (in kΩ) of the MOSFET is_________

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For the NMOSFET in the circuit shown, the threshold voltage is Vth , where Vth > 0. The source voltage VSS is varied from 0 to VDD. Neglecting the channel length modulation, the drain current ID as a function of VSS is represented by ##### Show Answer

In a MOS capacitor with an oxide layer thickness of 10 nm, the maximum depletion layer thickness is 100 nm. The permittivities of the semiconductor and the oxide layer are εs and εos respectively. Assuming εsox= 3, the ratio of the maximum capacitance to the minimum capacitance of this MOS capacitor is _____________.

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Which one of the following process is preferred to form the gate dielectric (SiO2) of MOSFETs ?

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If the base width in a bipolar junction transistor is doubled, which one of the following statements will be TRUE?

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The current in an enhancement mode NMOS transistor biased in saturation mode was measured to be 1 mA at a drain-source voltage of 5 V. When the drain-source voltage was increased to 6 V while keeping gate-source voltage same, the drain current increased to 1.02 mA. Assume that drain to source saturation voltage is much smaller than the applied drain-source voltage. The channel length modulation parameter $\lambda$ (in V-1) is ______.

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An npn BJT having reverse saturation current Is = 10-15 A is biased in the forward active region with VBE = 700 mV. The thermal voltage (VT) is 25 mV and the current gain ($\beta$) may vary from 50 to 150 due to manufacturing variations. The maximum emitter current (in μA) is _____.

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For a BJT the common base current gain α = 0.98 and the collector base junction reverse bias saturation current ICO  = 0.6μA. This BJT is connected in the common emitter mode and operated in the active region with a base drive current IB=20μA. The collector current IC for this mode of operation is

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In a uniformly doped BJT, assume that NE, NB and NC are the emitter, base and collector dopings in atoms/cm3, respectively. If the emitter injection efficiency of the BJT is close unity, which one of the following conditions is TRUE?