Finding Thevenin Equivalent Circuit for BJT Problem

[michaelface]

Homework Statement

The question asks to find the Thevenin equivalent circuit as shown in the attachment. (It's a BJT problem, but I'm having difficulty with the first part).

Homework Equations

Where are terminal points I need to worry about when making it an open circuit? That's the biggest question I have.

The Attempt at a Solution

I was able to find the equivalent resistance via R1||R2 + R3, but I don't understand how to find the voltage. Thanks for any help.

michael.

 

[n.karthick]

From the figure it seems that the base terminal connection of transistor is the one where you have to make open circuit.
And you have got correctly the Rth by doing so. Now you have to find Vth at the same terminal (i.e, just find voltage at base terminal which is of course open circuited)

 

[michaelface]

From the figure it seems that the base terminal connection of transistor is the one where you have to make open circuit.
And you have got correctly the Rth by doing so. Now you have to find Vth at the same terminal (i.e, just find voltage at base terminal which is of course open circuited)

So would the open circuit voltage be the same as if I were to calculate the voltage at point A? And I suppose that would mean it has to be the voltage with respect to ground. ie. [PLAIN]http://dl.dropbox.com/u/1981615/Vth.gif

Thanks a lot for your help.
michael.

 

[n.karthick]

Yes, that would be the Thevenin voltage for this circuit.

 

[michaelface]

Thanks for you help!
michael.