Re: [理工] [電子]-電晶體求VB的問題

[kevinztw (Kevin)]

※ 引述《fairwarning (一輪明月與藍夜!!)》之銘言：
: [電路圖]
: http://www.wretch.cc/album/show.php?i=fairwarning&b=73&f=1071644348&p=14
: [題目]
: The transistor in the circuit has a very high β.
: Find the highest value of VB for which the transistor still
: operates in the active region.

1. has a very high β => 忽略base電流 => Ie=Ic

2. transistor still operates in the active region
     => 假設電晶體剛好進入飽和區 => Vce=0.2V

3. Ve = (9-0.2)/2  因為Ie=Ic 所以上下兩個1k的電阻跨壓必定相等
                   所以9V減去Vce,sat後必定等量分布在兩個電阻上

4. Vb = Ve + 0.7 = 4.4 + 0.7 = 5.1V
     最後因為假設Vbe=0.7算出base電壓即是答案

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→ QQkimi:Vce=0.2? 我還以為是0.3XD
→ QQkimi:現在製程應該不都是0.3左右嗎?@@
推 jamtu:這題目會給吧 XD
→ QQkimi:j大3點半還在當遊魂= =
推 fairwarning:抱歉..我的課本答案是4.85..還是是我的課本答案錯了呢
→ fairwarning:不過也謝謝您的解答喔
→ fairwarning:您好..4.85V是BC逆偏算出來的....也謝謝您的熱心喔