An n-p-n transistor is used as a simple voltage amplifier in common emitter mode. when a signal of 30mV is added to base emitter voltage results a change in base current by 40 micro ampere and collector current changes by 2 mA given that the load resistance is 5 `k omega` calculate
(i) current gain
(ii) input resistance
(iii) transconductance
(iv) voltage gain

Explanation

Given `Delta V_(BE) = 30 mV`
`triangleI_(B)=40 muA`
`triangleI_(c )=2 mA`
(i) `beta =(triangleI_(c ))/(triangleI_(B ))=(2mA)/(40muA)=(2xx10^(-3))/(40xx10^(-8))=50`
(ii) input resistance `R_(BE)=(triangleV_(BE))/(triangleI_(B))`
`=(30mV)/(40 muA)=750 omega=0.75 komega`
(iii) Transconductance =`(triangleI_(C ))/(triangleV_(BE))`
`=(2mA)/(30mV)=0.67 omega^(-1)`
(iv) change in output voltage `triangle v_(0)=R_(I)triangleI_(c ))`
applied signal voltage =30 mV
voltage again `A_(v)=(10V)/(30mV)=333.33 V`