Question

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 positive terminal of a 8 V battery is connected to the collector through a load resistance ` R_L ` and to the base through a resistance ` R_B ` . The collector - emitter voltage ` V_(CE) = 4 V` , the base - emitter voltage ` V_(BE) = 0.6 V` and the current amplification factor ` beta = 100 ` . Calculate the values of ` R_L ` and `R_B` .

Answer 1

Given:`V_(CE)=4V, V_(BE)=0.4V. Beta=100`
`DeltaI_(C )=4mA=4xx10^(-3)A`
`V_(CE)+DeltaI_(C)R_(L)=V_(CC)`
`4xx10^(-3)R_(L)=8-4=4`
`R_(L)=1000Omega`
`I_(B)=I_(C)//beta=(4xx10^(-3))/(100)=4xx10^(-5)A`
`V_(CC)=I_(B)R_(B)+V_(BE)`
`8=I_(B)R_(B)+0.6`
`I_(B)R_(B)=7.4V`
`4xx10^(-5)R_(B)=7.4`
`R_(B)=(7.4)/(4)xx10^(5)=1.85xx10^(5)Omega=185kOmega`