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1 已知電晶體直流偏壓電流 IBQ = 20μA、β = 200 及VT = 26mV ，若輸入交流電壓 vbe = 13mV，則交流輸出電流ic？
A 1mA
B 1.5mA
C 2mA
D 4mA
  

`r_π` = `V_T/I_(BQ)`

= `(26m)/(20μ)`

= 1.3kΩ

交流 `i_b` = `v_(be)/r_π`

= `(13m)/(1.3k)`

= `10μ`

`i_c` = `β * i_b ` = `200*10μ`

= 2mA