# solve this question plz

Discussion in 'General Electronics Chat' started by munna007, Jun 18, 2010.

1. ### munna007 Thread Starter Active Member

Jul 23, 2008
51
0
hello to all....

i m having some doubts in solution of this question....

what i know about this ckt is that this is pnp transistor. +9 volt is connected to emitter (where arrow made) and -9 volt is connected to collector.

i think voltage emitter Voltage Ve should be equal to +9 volt , because current source is not dropping any voltage . but in solution part its found something else i.e 1.68 ....

why is it ???? plz clear my doubt

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2. ### munna007 Thread Starter Active Member

Jul 23, 2008
51
0
sory moderator for posting two times mistakenly .....

3. ### R!f@@ AAC Fanatic!

Apr 2, 2009
9,652
1,110
that is not the Ve voltage.
It is the Vce Voltage. Collector emmiter voltage

4. ### Ron H AAC Fanatic!

Apr 14, 2005
7,018
682
You are mistaken. The currrent source provides 1mA, regardless of the voltage across it. It does not have to be zero. In fact, the only way for the voltage across a current source to be zero is if it is paralleled by a zero ohm resistor (short circuit), or if (in this case) another 9V source were connected to the bottom end of it.

5. ### munna007 Thread Starter Active Member

Jul 23, 2008
51
0

in above lines , do u mean that in this circuit current source is not droping any voltage ????

by connecting another + 9 v at other terminal ,current will not flow . but if we connect -9v then current wil flow. m i right ????

6. ### Ron H AAC Fanatic!

Apr 14, 2005
7,018
682
An ideal current source can deliver current through a short circuit across it.
However, that is not the issue here. You said
Maybe I should ask why you think the current source is not dropping any voltage.

7. ### munna007 Thread Starter Active Member

Jul 23, 2008
51
0
i agree dear that current source has some voltage drop across it...

but the logic is not clear to me , i have never studied it in any book ????

8. ### Ron H AAC Fanatic!

Apr 14, 2005
7,018
682
A current source is the dual of a voltage source.
An ideal voltage source can maintain constant voltage, independent of the current through it.
An ideal current source can maintain constant current, independent of the voltage across it.

9. ### munna007 Thread Starter Active Member

Jul 23, 2008
51
0
thanks sir , u have really helped me a lot.....