Download Lab 3.8 Impedance of test instruments (p79)

Week 2: Diodes and Transistors
Lab 3.8 Impedance of test instruments (p79)
Yes, you are supposed to do 3.8 before 3.7, since it is related to last week’s material.
Now is a good time to review last week’s lecture on the input and output impedance.
Follow the instructions in the lab manual for lab 3.8 (p79). Answer the following
questions in your report:
1) What is the input resistance of your benchtop multimeter in voltage reading
mode for a DC (zero frequency) input? Describe your method, sketch your setup,
and show your calculations.
2) Do the same for channel-1 of your oscilloscope in DC coupling mode with input
scaling of 1 volt per division and a 100 Hz input signal from your signal
generator.
3) How does the oscilloscope input impedance change when you increase the input
signal frequency to 10 kHz? Your scope input can be modeled as an R and C in
parallel: what are the values of R and C? Show your calculation.
4) What is the output impedance of your signal generator when it outputs a 1V
peak-to-peak (p-p) 1 kHz sine wave signal with no DC offset? Describe your
method, sketch your setup, and show your calculations.
5) Skip the stuff in the lab manual about the 10X probe (but you are welcome to do
it and use a 10X probe if you have extra time on Wed).
Lab 3.7: Diode limiter (p78)
Reading: p61-70 “Diode circuits”
Note: The SM labels the diode as 1N914, it is the same as 1N4148 available in the
lab. The black band on the diode corresponds to the top of the arrow (ie cathode).
Follow the instructions in the lab manual for lab 3.7 (p78). Answer the following
questions in your report:
1) Sketch the input and output waveforms when you drive your diode limiter
circuit with sine, triangle, and square waves of different amplitudes (and no DC
offset).
2) Explain how the output depends on the amplitude and why.
3) What might this circuit building block be useful for?
Lab 4.2: Emitter follower (p95)
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Reading: p82-93 “Transistor circuits”
See also the hyperphysics notes on junction transistors: http://hyperphysics.phyastr.gsu.edu/hbase/solids/trans.html#c1
Follow the instructions in the lab manual for lab 4.2. Answer the following questions
in your report:
1) Sketch the input and output waveforms when you drive your emitter follower
circuit with a sine wave of different amplitudes (with no DC offset).
2) Explain the bumps below ground that you should be seeing with a large
amplitude input. (Hint: see VBE breakdown specification in the data sheet for
the 2N3904 transistor.)
3) Describe what happens when you connect VEE to -15V instead of ground.
Lab 4.3: Input and output impedance of follower (p95-96)
Follow the instructions in the lab manual for lab 4.3. Answer the following questions
in your report:
1) What is the emitter follower circuit's output impedance? Describe your method,
sketch your setup, and show your calculations.
2) What is the purpose of the 4.7uF "blocking cap" connected to the output?
3) What is the emitter follower circuit's input impedance? (Remember to
disconnect the 1K load so that it won't contribute). Describe your method, sketch
your setup, and show your calculations.
4) What is your transistor β?
Lab 4.7: Common-emitter amplifier (p98)
Follow the instructions in the lab manual for lab 4.7. Answer the following questions
in your report:
1) Calculate the voltage gain you expect from this amplifier circuit.
2) What is the purpose of the 0.33uF "blocking cap" connected to the input?
3) Sketch the input and output waveforms when you drive this circuit with a sine
wave. Measure the gain from these waveforms. Is there a phase shift from input
to output?
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