# A problem about two-port network.

Discussion in 'Homework Help' started by Feng Yu, Jun 20, 2015.

1. ### Feng Yu Thread Starter New Member

Jun 20, 2015
5
0

Circuit as the picture shows,with the independent current source generate current 2V1.
Need to find the admittance matrix Y.
{I1=Y11*V1+Y12*V2
I2=Y21*V1+Y22*V2

2. ### The Electrician AAC Fanatic!

Oct 9, 2007
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MOD NOTE: Link to forum sticky corrected.

Last edited by a moderator: Jun 20, 2015
3. ### Feng Yu Thread Starter New Member

Jun 20, 2015
5
0

In a) case,set V1=0,
I2=-I1,V2=5*I2 ====>Y12=-1/5 and Y22=1/5
But in case b) V2=0,
I dont know if the indepen current generator still effect to the circuit,or it just be opened.

4. ### WBahn Moderator

Mar 31, 2012
18,079
4,917
How do you figure that it is an independent current source? It seems like the current is dependent of V1, does it not?

5. ### WBahn Moderator

Mar 31, 2012
18,079
4,917
It is NOT an independent current generator. You should have been through analyzing circuits that have dependent sources LONG before you got to two-port networks.

You simply have a circuit that has a voltage-controlled dependent current source. So set up the mesh and/or node equations that govern it.

6. ### Feng Yu Thread Starter New Member

Jun 20, 2015
5
0
My fault,its a voltage-controlled dependent current source.
But what I meas is I don't know if the 2V1 source provides the current to the node or it's opened.

Let me clear my question:

I1+I2=0
or
I1+I2+2V1=0
?

7. ### WBahn Moderator

Mar 31, 2012
18,079
4,917
You have three currents coming into the top node.

Your first equation requires that the current coming out of the dependent current source be zero.

If that is the case, what does that require that V1 be?

If V1 is not zero, then (2 A/V)·V1 is not zero, right? If that's the case, then how can your first equation be valid?

8. ### Feng Yu Thread Starter New Member

Jun 20, 2015
5
0
Thanks,I got it.
I confused with the wire rightside.