作者kevinztw (Kevin)
看板Grad-ProbAsk
标题Re: [理工] [电子]-电晶体求VB的问题
时间Sun Nov 8 00:00:42 2009
※ 引述《fairwarning (一轮明月与蓝夜!!)》之铭言：
: [电路图]
: http://www.wretch.cc/album/show.php?i=fairwarning&b=73&f=1071644348&p=14
: [题目]
: 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电流 => Ie=Ic
2. transistor still operates in the active region
=> 假设电晶体刚好进入饱和区 => Vce=0.2V
3. Ve = (9-0.2)/2 因为Ie=Ic 所以上下两个1k的电阻跨压必定相等
所以9V减去Vce,sat後必定等量分布在两个电阻上
4. Vb = Ve + 0.7 = 4.4 + 0.7 = 5.1V
最後因为假设Vbe=0.7算出base电压即是答案
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 220.139.130.104
1F：→ QQkimi:Vce=0.2? 我还以为是0.3XD 11/08 00:14
2F：→ QQkimi:现在制程应该不都是0.3左右吗?@@ 11/08 00:18
3F：推 jamtu:这题目会给吧 XD 11/08 03:30
4F：→ QQkimi:j大3点半还在当游魂= = 11/08 07:44
5F：推 fairwarning:抱歉..我的课本答案是4.85..还是是我的课本答案错了呢 11/08 19:11
6F：→ fairwarning:不过也谢谢您的解答喔 11/08 19:11
7F：→ fairwarning:您好..4.85V是BC逆偏算出来的....也谢谢您的热心喔 11/08 19:25