CBSE Class 12 · 2017 · Delhi · SemiconductorsShort Answer

For a CE-transistor amplifier, the audio signal voltage across the collector resistance of 2 k

Ω

is 2 V. Given that the current amplification factor of the transistor is 100, find the input signal voltage and the base current, if the base resistance is 1 k

Ω

Answer: $I_{b} = 10 μ A$ ; $V_{in} = 10 mV$ .

Solution

Collector current:

I_{c} = \frac{V _{out}}{R _{c}} = \frac{2}{2 \times 1 0 ^{3}} = 1 \times 1 0^{- 3} A = 1 mA .

Base current (current gain

β = I_{c} / I_{b} = 100

I_{b} = \frac{I _{c}}{β} = \frac{1 \times 1 0 ^{- 3}}{100} = 1 \times 1 0^{- 5} A = 10 μ A .

Input signal voltage:

V_{in} = I_{b} R_{b} = (1 \times 1 0^{- 5}) (1 \times 1 0^{3}) = 1 \times 1 0^{- 2} V = 10 mV .

I_{b} = 10 μ A, V_{in} = 10 mV

CBSE Class 12 Board · 2017 · Delhi · Subjective

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