Electrical – Thevenin equivalent for a transistor circuit

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I'm having trouble with this circuit and was wondering if someone could help me. So far I know that the 20V source can be basically ignored since it is a NPN transistor here. The second circuit here is where I've gotten so far, but I'm not sure of all the values. I'm not sure what the value of the lower resistor should be. Is it still just 1k or is there something I'm missing?

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Best Answer

This question makes only sense if you have a linear circuit. I.e. you have to replace your non-linear diode by a linear model: this can be done if you assume that it is always forward biased and use a very simple diode model: a constant 0.6V voltage source.

Here are successive simplification steps turning your circuit into a linear circuit that consists of 2 resistors, 3 independent voltage sources and 1 dependent current source.

schematic

simulate this circuit – Schematic created using CircuitLab

Now just find its Thevenin equivalent (e.g. by applying two different test voltages and determining the current).

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