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JEE Main 2019 (12 Jan, Shift 2) · Junction Transistor

Junction Transistor question from JEE Main 2019 (12 Jan, Shift 2)

Q88JEE Main 2019 · 12 JAN · SHIFT 2Difficult

Junction Transistor

In the figure, given that VBB supply can vary from 0 to 5.0 V, VCC = 5V, β\betadc = 200, RB = 100 kΩ\Omega, RC = 1 kΩ\Omega and VBE = 1.0 V. The minimum base current and the input voltage at which the transistor will go to saturation, will be respectively:

Figure

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Answer: (d)

  1. At saturation VCE≈0V_{CE} \approx 0: IC=VCCRC=5 V1 kΩ=5 mAI_C = \dfrac{V_{CC}}{R_C} = \dfrac{5\ \text{V}}{1\ \text{k}\Omega} = 5\ \text{mA}
  2. Minimum base current: IB=ICβ=5 mA200=25 μAI_B = \dfrac{I_C}{\beta} = \dfrac{5\ \text{mA}}{200} = 25\ \mu\text{A}
  3. Input voltage: VBB=IBRB+VBE=25 μA×100 kΩ+1=3.5 VV_{BB} = I_B R_B + V_{BE} = 25\ \mu\text{A} \times 100\ \text{k}\Omega + 1 = 3.5\ \text{V}
  4. So the answer is (d) 25 μA25\ \mu\text{A} and 3.5 V.
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