Week #8: (10/23-27) Transistor Biasing

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rjagodowski
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Week #8: (10/23-27) Transistor Biasing

Post by rjagodowski »

This week we'll continue to discuss some of the circuits investigated in the Transistor Biasing Lab from Week #7.

A key point to keep in mind during this discussion: The current gain parameter, beta (also known as hFE), generally has a wide range of values within a specific part number. For example, small signal transistors like the 2N3904 & 2N2222 may have a beta range between 50 to 300. One goal of the various biasing circuits we are discussing is to stabilized the bias point, known as the Q-point, with respect to variations in beta.

We will begin analyzing a Common Emitter Voltage Divider Biased NPN transistor amplifier for A.C. operation. The example we will work through is the one presented in our Week #9 lab experiment. Check out this link for information about the r-parameter Transistor Model.

We will also discuss some of the parameters for the 2N2222A transistor's spec sheet, specifically those dealing with beta (hFE on the sheet). Here is the pdf for the 2N2222 transistor in the TO-92 package:
2N2222A-Datasheet.pdf
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