Help pls

139

01:14:31

Can anyone help me figure out the calculations which led to these results? All I’ve given is beta1=beta2=100 , vbe1=vbe2=0.7V 

published 3 years ago

Robert_Kidd

3 years ago

First tell us what the circuit function is meant to be and where you got it from.

592azy2circuitdude

3 years ago

I found a way solve it. Are you familiar with the Node-Voltage method? I'm not sure how much help you need, but hopefully this will get you started.

592azy2circuitdude

3 years ago

There are 4 unknown nodes in the circuit. Use KCL to find the 4 node voltage equations. Then use the equations relating base and collector currents for both transistors. Use KVL to find an equation relating 2 of the node voltages to the Vbe of the top transistor. Lastly use Ohms Law to find an equation for Ib for the bottom transistor (current through 1k resistor).

592azy2circuitdude

3 years ago

When the dust settles, you will end up with 8 equations with 8 unknowns (yikes!). If you solve these simultaneously, you will have the solutions (this is actually a rather hard circuit to calculate).

592azy2circuitdude

3 years ago

One last thing. The calculations will not perfectly match the simulation. This is because the simulator uses a more accurate method to find Vbe for the transistors instead of assuming they are a constant 0.7V. I hope this helps. Good luck!

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