A bipolar junction transistor has common base current gain of 0.99 and collector base reverse saturation current of 1 μA. If it is operated with base current of 50 μA in common emitter configuration, what will be collector current?

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  1. 50.5 μA
  2. 5.05 mA
  3. 4.95 mA
  4. 5.00 mA

Answer (Detailed Solution Below)

Option 3 : 4.95 mA
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Detailed Solution

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Explanation:

Key Formula:

  • Collector Current (IC) in common emitter configuration: IC = β × IB + ICBO
  • Where:
    • β = Current gain in common emitter configuration (related to α)
    • IB = Base current
    • ICBO = Collector-base reverse saturation current

Given Data:

  • Common base current gain (α) = 0.99
  • Collector-base reverse saturation current (ICBO) = 1 μA
  • Base current (IB) = 50 μA

Step-by-Step Calculation:

1. Relation between α and β:

In a BJT, α and β are related as follows:

β = α / (1 - α)

Substitute the value of α:

β = 0.99 / (1 - 0.99)

β = 0.99 / 0.01 = 99

2. Collector Current (IC):

Using the formula:

IC = β × IB + ICBO

Substitute the values:

IC = 99 × 50 μA + 1 μA

IC = 4950 μA + 1 μA

IC = 4951 μA

Convert μA to mA:

IC = 4.951 mA

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