Please go to update pages for the latest modification, class-wise issues, and others if links for those pages exist.
update page a  update page b   update page c

Lab work modification: - Do Part 0 ( Introduction), Part 1 (Instrumentation), and Part A only (three parts total): do everything, including answering/discussion all questions. - Experimental work of Part B and C are not required: It means no circuit, no measurement needs be done. You are required to only observe and write a report of your understanding, thoughts, and summary of these Parts. This should be put at the end of your report, a synthesis of everything that you learn in Lab 4. Create a subsection, titled "Report on observation of Parts B and C demonstrations". Do not mix this with what you summarize for your work in Part A. However, if you do anywork along the line of Part B and Part C, you are welcome to include for extra credit.

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Research questions:

Based on the discussion above, we see that op amp can be used as a dependent source to certain extent (i. e. within certain limits), and which you will verify in your lab work. However, do you think that there is such a thing as an ideal dependent source that is absolutely "faithful" or has perfect fidelity with respect to the control input (the source that it depends on)? This leads to the key research questions below, which have a more important and wider implication beyond this lab that you should learn.

How can one use the operational amplifier (op amp) as a dependent source, and how "dependable" is the "dependent" source? What concepts, criteria can one introduce as metrics - or figures-of-merit for the "dependability" of a dependent source? (Here, we will explore the concept of signal "fidelity" such as the "fi" in "hi-fi" equipment, and the concept of temporal causality and frequency response).

Components:

You will need:

1. One LM741 for each circuit. If you have a dual, or quad op-amp IC chip, then you need only one IC.
2. Assortment of resistors as indicated in the circuits.
1. For Circuit B: 1 kOhm, 10 kOhm, 27 kOhm, 100 kOhm (gain of 10, 27 and 100, or 10 dB, 14.3 dB, and 20 dB for amplitude). The highest gain, 20 dB is only necessary to amplify the small photodiode signal.
2.  For Circuit A: a 2.7 kOhm (strong light signals) or 10 kOhm (weak light signals).
   
3. A photodiode for Circuit A, and also a LED so that you can generate an optical signal to test your photosensor. The photodiode is a Silicon PIN, it looks like this, , here is the data sheet. Any LED will do. You are also encouraged to bring in a remote control from home so that you can see how and what "sms" a remote control "talks" to a piece of equipment.
4. A small black box or some thick black paper to be rolled up into a dark tube or something equivalent to shield the photodiode from strong ambient light. You can make a small hole so that your test light sources can be coupled in.
   

Main app for the Lab:

There is only one app to help you review some basic concepts of periodic signal while you are exploring how to use the function generator and the oscilloscope.


For those who have learned about Fourier analysis, there is an app for you to analyze signals, such as your voice, using computer.

Basic app: Review basic concepts of a sinusoidal function. Simulate features seen on the function generator and the oscilloscope.	Use the same App, click the phasor button to learn or review phasor concept if you need a refresher.
Fourier analysis.

Lab work:

Step 1 - Check out the function (signal) generator and oscilloscope

Please follow step-by-step instructions of this presentation  .

Verify that you can generate the signals in the table below and and observe them on the oscilloscope. You can choose any amplitude as you wish between 0.1-V peak-to-peak to 2-V peak-to-peak (roughly). Leave the DC offset at ~zero V. Sketch this table in your lab notebook, and just make a check mark in each box that you have done.

(signal type/frequency)	500 Hz	5 kHz	10 kHz	50 kHz	100 kHz	500 kHz
sine
square
ramp

Draw in the lab notebook what you observe on the oscilloscope INCLUDING the amplitude and time scales for a 10-kHz square signal such that the viewer can infer the amplitude and frequency of your signal and reproduce it with a function generator. If you do not wish to draw, we'll accept if you:
- take a picture, print, crop to show only the oscilloscope, and paste.
- or save the waveform (.csv) on a USB drive (or link directly to your computer if you have a driver to communicate with it), use any graphics software to plot, print, and paste. Important: you cannot take the data from another team and pass it on as your own.

Step 2 - Set up your power supply to give +15 V, -15 V, and ground.

Step 3 - Build Circuit B (see page 1)

Build circuit B. Choose input resistor be 1 kOhm. Set up for 3 feedback resistors (Rfb): 10, 27, and 100 kOhm so that you can switch gain.  Do not turn on your power supply yet until you finish and double check on the wiring.

See the pin layout below of LM741. Please make sure it is correct before turning on your +-15 V power supply.

Step 4 - Measurements of signal gain and phase shift

4.1 Connect the inverting-input wire to the Rfb = 10 kOhm. You should have a gain of 10 (10 kOhm/1 kOhm).

4.2  Generate a sine wave signal with f=500 Hz, 0.2-V peak-to-peak (see what you did in Step 1 above), and DC offset=0 V. Use a T-splitter to monitor the signal on a channel of the oscilloscope. The other split signal is connected to the input of Circuit B. Connect the output of Circuit B to another channel of the oscilloscope. You should see two signals: input and output.

4.3 Sketch in your lab notebook the signals with amplitude, OR capture the scope output with a USB stick, plot, print & paste (ppp) into your lab notebook. Determine the gain according to the formula:
                           

below is an example how you can calculate the gain:

Note that "amplitude" here always means the absolute value of the amplitude. If a signal is negative, we let the minus sign be its phase, which is ±Pi.

4.4 Use the scope built-in function to measure the phase shift (or phase difference) between the signals. Refer to the app in page 1 for the convention about the sign of the phase shift.

4.5 Change the gain by switching the feedback resistor wire that is connected to the 10-kOhm Rfb resistor to the 27-kOhm Rfb. Do steps 4.3 and 4.4 again

Step 5 - Measurements of amplifier output saturation

5.1  Slowly increase the signal amplitude from 0.2-V p-p to 2-V p-p. At which point do you observe tell-tale sign of amplitude saturation? Report this in your lab notebook.

5.2 Sketch in your lab notebook the signals with 2-V p-p on the scope, OR capture the scope output with a USB stick, ppp (plot, print & paste) into your lab notebook (the saturation clip-off at high and low voltage should be very obvious, if not there must be something wrong).

Step 6 - Measurements of amplifier bandwidth (see above)

6.1  Reset the signal amplitude to 0.2-V p-p (still 500 Hz). You can choose either Rfb=27 kOhm or 10 kOhm. Write down the output signal amplitude.

6.2 Change the frequency from 500 Hz to 500 kHz as what you did in Step 1 above. At each frequency, measure the output signal amplitude, calculate the gain in dB according to the formula in 4.3. Then plot your data of gain vs. frequency on log-dB scale (frequency on log scale and gain(dB) on linear scale). Draw a curve fitting through the data and mark the point where you think the gain is approximately -3dB of the beginning (500 Hz). The frequency at this point is called the 3dB bandwidth. -3dB ~ 1/2. It means your output signal at that frequency is only ~ 1/2 of that at the lowest frequency.

6.3  Set the frequency at twice the 3dB bandwidth (e. g. if your 3-dB bandwidth is 120 kHz, generate a signal at 240 kHz), select square-wave output (leave amplitude alone, which should be ~ 0.2 V p-p). Sketch the waveform you see on the scope, or acquire them via USB, ppp into your notebook. Discuss what signal distortion you observe between the input and output.

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