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An n-p-n transistor in a common emitter mode is used as a simple voltage amplifier with a collector current of 4 mA. The terminal of a 8 V battery is connected to the collector through a load resistance R_(L) and to the base through a resis-tance R_(B). The collector- emitter voltage V_(CE)=4V, base-emitter voltage V_(BE)=0.6Vand base current amplification factor beta_("d.e.")=100. Calculate the values of R_(L) and R_(B) |
Answer» Solution :Potential difference across `R_(L)`  `=8V-V_(CE)=8V-4V=4V`. Now `I_(C)R_(L)=4V` `R_(L)=(4)/(4XX10^(-3))=10^(3)Omega=1kOmega` Further for base emitter equation, `V_(C C)=I_(B)R_(B)+V_(BE)` or `I_(B)R_(B)=` Potential difference across `R_(B)` `=V_(C C)-V_(BE)=8-0.6=7.4V` Again, `I_(B)=(I_(C ))/(beta)=(4xx10^(-3))/(100)=4xx10^(-5)A` `THEREFORE R_(B)=(7.4)/(4xx10^(-5))=1.85xx10^(5)Omega=185kOmega` |
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