Analyzing a Current Mirror: Finding Rref for Vcc=8V and Icopy=0.38mA

AI Thread Summary
To find Rref for a current mirror with Vcc=8V and Icopy=0.38mA, it is assumed that the base current (IB) is negligible due to a high beta value of the transistor. This assumption allows for simplification in calculations, although IB is not exactly zero. The discussion clarifies that while the base current can be ignored, it is not completely absent. The correct approach acknowledges the relationship between collector and base currents in high beta transistors. Understanding these transistor dynamics is crucial for accurate circuit analysis.
Cocoleia
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Homework Statement


I am working on this problem. They start out by giving me:
upload_2017-9-25_20-44-28.png

I am asked to find Rref such that Vcc=8V and Icopy=0.38mA.

Homework Equations


Transistor equations

The Attempt at a Solution


In this case, they never specify if IB=0A (sometimes it does ?) but I would assume that it is and therefore beta would be very large and we ignore this.

upload_2017-9-25_20-51-11.png
 
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That's the answer I got.
 
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Cocoleia said:
In this case, they never specify if IB=0A (sometimes it does ?) but I would assume that it is and therefore beta would be very large and we ignore this.

Right answer but you have the explanation backwards...

Beta is high so the base current is much smaller than the collector current. Therefore the base current can be ignored (but the base current isn't zero).
 
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