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CBSE Class 12-science Answered

For a common emitter amplifier, the audio signal voltage across collector resistance 2 kΩ is 2V. If the current amplification factor of the transistor is 200 and base resistance is 1.5Ω, the input signal voltage and base current are
Asked by Topperlearning User | 10 Jul, 2014, 01:52: PM
Expert Answer

The collector signal current ic is given by

ic = vc/Rc = 2V/2kΩ = 1 mA

Since the current amplification (βac) of the transistor is 200, the base signal current ib is given by 

ib = ic/βac =1 mA/200 = 0.005 mA = 5μA

The input signal is the voltage drop (ibRb) produced across the base resistance by the flow of the base current.

Therefore, the input signal voltage = ibRb = 5μA x 1.5 kΩ = 7.5 x 10-3 V =0.0075 V.

Hence the input signal voltage = 0.0075 V and the base current = 5μA.

Answered by | 10 Jul, 2014, 03:52: PM

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