Analog electronics (BJT circuit analysis)

  • #1
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Homework Statement


upload_2016-12-9_20-6-1.png

For beta = 100 and assuming ro is very large, what is the DC voltage at the collector?

Homework Equations


IB = IE(β+1)

IC = β*IB

The Attempt at a Solution


Since IE = 0.5mA, IB = 0.0505 A
Then, IC = 5.05 A (which doesn't feel right)
VC is the same potential across the 30kΩ load?
I tried doing KCL with those currents (to find the current thought the load resistor).
Should I not be analyzing the direct circuit--should I make an equivalent T-model?
 

Answers and Replies

  • #2
Charles Link
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Homework Statement


View attachment 110203
For beta = 100 and assuming ro is very large, what is the DC voltage at the collector?

Homework Equations


IB = IE(β+1)

IC = β*IB

The Attempt at a Solution


Since IE = 0.5mA, IB = 0.0505 A
Then, IC = 5.05 A (which doesn't feel right)
VC is the same potential across the 30kΩ load?
I tried doing KCL with those currents (to find the current thought the load resistor).
Should I not be analyzing the direct circuit--should I make an equivalent T-model?
Your equation should read ## I_E=I_B (\beta+1) ##. Try again. I think you also need to assume ## V_{BE}=.7 \, volts ## (approximately). One hint for you: The capacitors basically block any steady state current trying to go through them so the capacitor is an open circuit for the DC part of the analysis.
 
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