Module Lab Exercise: Determine Beta for BJTs
Wire the circuit shown, with Rc = 470 ? and Q = 2N3904
? Record Ib and Ic in the table below for the given values of RB
? Calculate the base current IB from (9 V - Vbe)/RB
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RB
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Ib
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Ic
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Vbe
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Vce
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Beta
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1M?
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470K?
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200K?
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100K?
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47K?
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? Start with RB = 1 Mohm, then continue with the RB values.
(A) Squeeze the transistor between your fingers to raise the case temperature, record any change in collector current.
(B) Put a piece of ice in a plastic bag and hold it on the transistor to reduce the case temperature, record any change in collector current.
? Describe your perception of the relationship between Beta and case temperature.
? Describe the behavior of Beta vs Ic.