lab1 - Experiment-1 Experiment-1 Bipolar Junction...

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Experiment-1 R. B. Darling EE-332 Laboratory Handbook Page E1.1 Experiment-1 Bipolar Junction Transistor Characterization Introduction The objectives of this experiment are to observe the operating characteristics of bipolar junction transistors (BJTs). Methods for extracting device parameters for circuit design and simulation purposes are also presented. Precautions Bipolar junction transistors do not employ a fragile, thin gate oxide like MOSFETs do, and they are thus much more robust against electrostatic discharge (ESD) damage. Since all three leads of the BJT are interconnected by internal pn-junctions, small charges can bleed off through the leakage currents of these junctions, and static charges are soon dissipated internally. For these reasons, BJTs can usually be handled freely, and are rarely damaged by ESD. This makes them very pleasant to work with.
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Experiment-1 R. B. Darling EE-332 Laboratory Handbook Page E1.2 Procedure 1 BJT base lead and sex identification Set-Up Locate a type 2N3904 BJT from the parts kit. This should be a three lead device in a small plastic TO-92 package. Turn on a bench DMM and configure it to measure (two wire) resistance. Plug a black squeeze-hook test lead into the negative ( ) banana jack of the meter and a red squeeze-hook test lead into the positive (+) banana jack of the meter. The objective of this procedure will be to determine which lead of the BJT is the base, and whether the BJT is an npn or pnp device using only the ohmmeter function of the DMM. Also locate a 1N4148 diode that will be used for reference. Measurement-1 Measure the resistance of the 1N4148 diode with the DMM in both the forward and reverse bias directions. Note that the red lead from the (+) input of the DMM is the one which will have the more positive voltage for this type of test. Record these readings in your lab notebook, and note these readings as being “typical” for a forward and reverse biased pn-junction. You can then refer to these readings to determine the polarity of pn-junctions that exist within the BJT. Recall that a BJT has pn-junctions between the base and both the emitter and collector terminals. Use the DMM in its ohmmeter setting to test pairs of leads on the BJT and therefore identify the base lead on the device. From the polarity which causes the base terminal to conduct, deduce whether the BJT is an npn or pnp device. With the base lead identified, it stands to reason that the remaining leads must be the emitter and collector. A few measurements will next be made to examine if these two remaining leads can be distinguished by DMM measurements. First, use the DMM, again in its ohmmeter setting, to measure the resistance between emitter and collector with the base terminal open circuited. Try this with both polarities of the DMM leads. Next, use the DMM to measure the resistance between emitter and collector with the base now connected to the ( ) lead of the DMM in addition to the other transistor lead that is already there. Again, try this in both polarity directions.
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lab1 - Experiment-1 Experiment-1 Bipolar Junction...

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