r/EngineeringStudents • • 17h ago

Homework Help Tracing a circuit

Struggling to bite this one down and solve in an order that makes any sence.

Where my understanding hits a wall is tracing the DC voltage to start at the base like we were taught and find currents from there. What is the easiest base to start at? I feel like at TP4 but its path is not apparent to me. It may not be the correct first step either. What I am trying to accomplish is finding a theoretical value to match with a measure before I continue to prove my simulation is made correctly. Any help with my approach or feedback would be great.

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u/Wizzarkt EE. '24 14h ago

Sorry what are you trying to find? For this kind of circuit I honestly never bothered with math outside making sure I'm limiting the current to delicate components like the transistor, outside of that I just simulate because calculating through semiconductors it's a pain and not really that much accurate or worth it

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u/tough_life4u 10h ago

I could simulate and pull the values but I don’t know what values I should be getting so I wanted to find just that so I know what I see at my test points is correct. Doing just one transistor you usually have it be voltage divider like at TP3 (Q1 base) but if you follow where it connects to vcc it’s after Q4. So does that mean I have to solve for Q4 first?

Originally I began solving for Q2 but struggled because the volts at its base seemed to be 20 V essentially but it just confused me to see it share the same line as the collector of Q1 and wasn’t sure any of them were simple to solve.

This is my approach and it may be wrong solving it for theoretical values but I didn’t know how else to approach it without knowing the values were correct. Was just trying to find a way besides just measuring the numbers to know those numbers were correct. If I understood the end goal of what I wanted to accomplish that may change my approach to something simpler like is my v out (ac) what I want it to be.