작성일 : 15-09-24 10:40
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Solution for Prob. 3.21
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글쓴이 :
최우영
 조회 : 1,084
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Prob. 3.21(b) that someone asked about today's class can be solved as following:
- Case 1: D1 ON and D2 ON
V_out = V_D,on for Iin>0 (Notice there is no current through R1)
- Case 2: D1 OFF and D2 ON
V_out = D_D,on for Iin>0
(This case is identical to Case 1)
- Case 3: D1 ON, D2 OFF
Vout = Iin x R + V_D,on (a)
For D2 off, Vout < V_D,on (b)
From (a) and (b), Iin < 0 but this cannot be true since D1 is On
==> This case can not be true
- Case 4, D1 OFF, D2 OFF
Iin cannot flow since it has no current path. Or Vout cannot be defined.
Considering above four cases, only Case 1 is possible.
Iin<0 cannot be possible since there is no current path.
In short, this is a bad problem.
A better problem would be adding a resistor (R2) in parallel with the current source. Then,
Vout = V_D,on when Iin > VD,on / R2 or
Vout = Iin x R2 when Iin < VD,on /R2
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