Questions about saturation mode in Tr
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작성자 박종서 댓글 2건 조회 620회 작성일 20-04-24 23:07본문
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2. In some figures and problems in the textbook, they say that the edge of saturation in Tr is when V_BC=0 (V_Base-V_Collector=0).
But I remember professor states that it is still active mode because V_CB(V_Collector-V_Base in npn) is not more than V_d,on=0.4V between base and collector.
If I understand it correctly, i guess that the difference of explanation is just because textbook doesn't consider V_d,on effect for simplicity. Am i right?
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정우진님의 댓글
정우진 작성일
2. Hmm... I reckon there are adequate infos in the textbook:) Look at the bottom of page 137, Microelectronics (of Razavi). There are some infos 'bout your question. It says we permit region of "soft-saturation" when V_BC < 400mV, adding some explanations. Moreover, there are a number of problems which are dealing with "soft-saturation" mode.
I hope this helps:)
TA님의 댓글
TA 작성일
1. Current gain (beta) is defined as a ratio of Ic over Ib, so the equation holds in the saturation mode.
2. In the active region of BJT operation, voltage between collector and the emitter is positive. However, in when Vbc < 400mV, where base-collector junction is about to be forward bias BJT still acts like to be in active mode, called soft saturation or quasi saturation.