# Learn About Thevenin Theorem and Dependent Source Circuits

Discussion in 'General Electronics Chat' started by grahamed, Oct 9, 2015.

1. ### grahamed Thread Starter Member

Jul 23, 2012
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11
Hi

I am not sure where to post this but.....

The article says that Vth and Rth are 10V66 and 0R888 respectively. I get 9V and 5R33333.

I could be wrong, I often am, but it seems hard to produce 0R888 out of 6, 8 and 10. It would seem that the lowest possible resistance, by any arrangement would be 6//8//10 = 2R66

Plot shows circuit loaded by my value of 5R33 and output being 4V5, unloaded output (Vth) is 9V. I dare say someone will point out my error.

2. ### Jony130 AAC Fanatic!

Feb 17, 2009
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If RL is R4 then
Rth = (10Ω+6Ω)||8Ω = 16/3 = 5.33Ω and Vth = 12V*(8Ω)/(10Ω + 6Ω + 8Ω) + (1.5A*10Ω/(6Ω+8Ω+10Ω))*8Ω = 9V

3. ### Jony130 AAC Fanatic!

Feb 17, 2009
3,993
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And where is this dependent source ?? Because this will change everything.

Jul 23, 2012
99
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5. ### grahamed Thread Starter Member

Jul 23, 2012
99
11
Am I missing the point? Is the dependent source being used solely as a method of analyzing the circuit, or what?

6. ### Jony130 AAC Fanatic!

Feb 17, 2009
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In this example author show as how to find a Vth and Rth when we have a dependent source in our circuit.
But your circuit do not have any dependent source, I see only two independent source. Do you even know what dependent source is?

Jul 23, 2012
99
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Probably not

8. ### grahamed Thread Starter Member

Jul 23, 2012
99
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This article seems to be about how to equate fig 2 to fig 1 and find values for Vth and Rth. No?

9. ### grahamed Thread Starter Member

Jul 23, 2012
99
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Ah is it saying the middle current source is 1.5 x Ix? I thought it said Ix = 1A5. If so Mea culpe.

10. ### Jony130 AAC Fanatic!

Feb 17, 2009
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Yes, but in the example the author used the Current-controlled current source (CCCS). And this current source delivers the current equal to 1.5 times the 6Ω (Ix) resistor current.

11. ### grahamed Thread Starter Member

Jul 23, 2012
99
11
Yes definitely my error

12. ### Jony130 AAC Fanatic!

Feb 17, 2009
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Here you have a LTspice file. And notice that Vth = 10.6667

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13. ### grahamed Thread Starter Member

Jul 23, 2012
99
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As I said I had definitely misunderstood. Thank you for your help.