Electronic Physics Lab 2011

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Electronic Physics Lab, Fall Semester 2011

-Weekly class schedule

08. 29 – 09. 04: Orientation

09. 05 – 09. 11: Lab 0 – Basic Devices, Lab 1 – RC Circuits

09. 12 – 09. 18: Thanksgiving week

09. 19 – 09. 25: Lab 2 – Diodes

09. 26 – 10. 02: Lab 3 – Basic DC Power Supply

10. 03 – 10. 09: Lab 4 – BPJ Transistor

10. 10 – 10. 16: Lab 5 – FM Wireless MIC kit

10. 17 – 10. 23: Mid-term exam.

10. 24 – 10. 30: Lab 6 – Op Amps: Open Loop, Inverting, Non-inverting

10. 31 – 11. 06: Lab 7 – Op Amps: Summing, Differential11. 07 – 11. 13: Lab 8 – Op Amps: Integrator, Differentiator

11. 14 – 11. 20: Lab 9 – Op Amps: Active Filters

11. 21 – 11. 27: Project – Feedback circuits



12. 12 – 12. 18: Final exam.

- Assignments (Lab 60 %, theory 40 %)

• Pre-report before the start of each experiment (10 %)• Oral presentation on the theory of each experiment (10 %): 10~15 min.

o Introduce the purpose and expectation of the experiment to be performed

• Experimental report for the previous experiment (40 %)

o Need to suggest raw data

o Respond to each item in the manual

• Oral presentation on the results of the previous experiment (20 % + 20 %): 15~20 min.

o Students will evaluate the presenter (20 %)

- Instructor and teaching assistants

• Instructor: Wonshik Choi, [email protected], room 405, office hour: Tuesday 2-4

• TA:이상엽 010-8835-5582, [email protected], 이학관 424

김윤호 010-9676-4674, [email protected], 이학관 626

최재혁 010-8712-3763, [email protected], 이학관 626

강필성 010-4261-0006, [email protected], 이학관 423B

mailto:[email protected]






















To get started:

1) Check the parts in the kits against the parts list. Report any shortages. It may be helpful to

label parts on a sheet of paper and attach them with masking tape. Learn to use the colorcode chart for resistors and become familiar with the pin outs of the parts.

2) Use your digital multimeter on the ohms scale to check which grounds are connectedtogether on the breadboard (5V GND, ±15V GND, BNC connector GND, etc.).

3) Plug in the test equipment and breadboard. Check and record the actual power supply

voltages on the breadboard.

4) Turn on the oscilloscope and get a trace by setting the trigger to auto and moving thevertical position knobs. Hook the scope up to the function generator and change the

manuals if necessary. Always know the capabilities and limitations of your test

equipment.5) Helpful hints and some rules:

- If you have access to wire cutters, wire strippers and needle nose pliers they will speedup construction of the circuits. Bring them to class.- You may wish to bring BNC cables and test leads of your choice. Be sure to mark them

to keep them separate from the ones provided.

- Keep your lab sheets, data sheets and your notes in a three ring binder. The labs build

on each other and you will need to refer back to completed labs.- Collaboration within your lab group and between groups is encouraged for all aspects of

the class. Interesting circuits will be drawn on the blackboards. Try to figure out what

they do and how they work.



Lab 0: Basic Devices

Analog Lab Unit

(1) Try to understand the characteristics and/or functions of each element of the unit.(2) Use a digital multimeter and check the values and/or functions of resistors, potentiometers,

switches, capacitors, DC source and AC source. Report if you find anything broken or

seriously deviated.

(3) Connect the output of the signal generator to the input of the frequency counter. Check if

both elements are working properly.

(4) Randomly choose 5 resistors from the pile. Read the color code and indentify the resistance.

Measure the resistance using a multimeter and compare with the color code reading.

(5) Apply DC 5V across any resistor and measure the current using the ammeter. Calculate the

current and check if the ammeter is working correctly. Change the voltage or the resistor if

necessary.



Lab 0: Oscilloscope and function generator

(1) If your oscilloscope does not have AUTOSET or PRESET function, then set the controls to

the standard positions as follows: Set the oscilloscope to display Ch 1; Set the Volts/Div scale

to a mid-range position; Turn off the variable Volts/Div; Turn off all magnification settings;

Set the Ch 1 input coupling to DC; Set the trigger mode to Auto; Set the trigger source to Ch

1; Turn trigger holdoff to minimum or off; Set the intensity control to a normal viewing level;

Adjust the focus control for a sharp display.

(2) Connect the output of a function generator to the input Ch 1 of an oscilloscope. Always use

BNC connectors with proper grounds.

(3) Generate various types of signal and observe the display. Adjust the focus and intensity if

necessary.

(4) Try to adjust the Volts/Div and the Sec/Div knobs and observe the changes in the curves.

Make sure you understand what you see in the display.(5) Apply the DC offset of the function generator. Change the coupling to AC and understand the

difference from DC coupling. Try ground coupling, too.

(6) Connect the signal generator output of the analogue lab unit to the input Ch 2 of the

oscilloscope. Try to display both channels on the sample display. Try alternate, chop, add, or

XY modes, and understand what each of them means. Utilize vertical controls.



Lab 1: RC Circuits

Voltage divider (attenuator)

(1) Form the circuit on your bread board.

(2) Using the 5 volt power supply as the SIGNAL SOURCE with the + terminal (red) to INPUT

and the – terminal (black) to COMMON, measure the OUTPUT voltage using your scope and

DMM with RL=∞; with RL=1K; with RL=100Ω; and with RL=0Ω.

- How does the measured OUTPUT voltage compare with the theoretical OUTPUT voltage?

- Account for the differences.

(3) With RL open (i.e. RL =∞), measure the current flowing through R1 and R2 using your

DMM.

- Calculate how much power is being dissipated by R1 and R2 (Note: P = V * I).

(4) Change resistors to R1=R2=10MΩ and RL=∞.

- Calculate what the OUTPUT voltage should be with a 5 volt input.

- Measure the OUTPUT voltage with scope and DMM. Explain the results.

(5) Keep R1=R2=10MΩ. Remove the 5 volts from the INPUT. Connect the function generator

connector BNC center pin to the INPUT and the outer ring of the generator connector (i.e.

shield) to COMMON.

- Using your scope, adjust the generator to give you a 2 Vp-p, 100Hz sine wave. Look at the

OUTPUT with your scope.

- Now vary the generator frequency from 10Hz to 1MHz. What do you observe on the scope?

- Explain the results.(6) Change R1=R2=1K. Now look at the OUTPUT with your scope and DMM across the

generators frequency range. Explain the results.



Lab 1: RC Circuits

Low pass filter (DC coupled circuit, AC blocking circuit)

(1) Form the circuit on your bread board.

(2) Using a sine wave from the function generator as an INPUT (10 Vp-p, peak-to-peak),

measure the INPUT and OUTPUT voltage from 10Hz to 100KHz using your scope and

DMM. Take at least three data points per decade of frequency.

- Do the two measuring devices agree? Explain the results.

- Calculate the decibel loss for each OUTPUT data point. Make a table for it.

(decibel) = 10 log (Vout /Vin)2

- Plot the data on the lin/log graph using the vertical axis for OUTPUT in decibels and the

horizontal axis for frequency in Hertz.

- What is the frequency with the decibel loss 3 dB (i.e. -3 dB)? This frequency is called (3 dB)cutoff frequency.

- What is the capacitive reactance at the 3 dB cutoff frequency?

- Using both channels of the scope, measure the phase shift form INPUT to OUTPUT at the 3

dB frequency.

- Do you have any phase difference? Discuss why you have that phase shift.

(3) Discuss how to make a high pass filter (that couples AC, but blocks DC).



Lab 2: Diodes

Small signal diode, general purpose rectifier diode

Forward bias

(1) Form the circuit shown in Fig. 1 on your bread board. Voltage should be set initially to 10 V.

(2) Adjust R1 so that the forward current IF = 0.5 mA, and measure the forward voltage VF

across the D1. Repeat the measurement while increasing the forward current up to 5.0 mA

with steps of 0.5 mA. Plot the result as a graph.

(3) Replace the diode with 1N4004, and repeat the step (2)

Reverse bias

(4) Remove the ammeter. Replace the diode with 1N4148 but with the polarity of the diode

reversed. Increase the supplied voltage to 15 V.

(5) Adjust R1 until the voltage across D1 is 12 V. Measure the voltage across R2 and calculate

the reverse current.

(6) Adjust R1 and repeat the measurement and the calculation. Plot the result on the same graph

with the forward bias case.

(7) Calculate the reverse resistance of the diode.

(8) Replace the diode with 1N4004, and repeat the steps (5) – (7).



Lab 2: Diodes

Zener diode

(1) Using the 1N5231B datasheet, find and record the nominal zener voltage (VZ or VZNM), and

zener test current (IZT).

(2) Construct the circuit shown in Fig. 2. VS should be set to 0 V.

(3) Adjust VS until the current is 1 mA. Measure and record the voltage across the zener diode.

Repeat the measurement for various current values up to 30 mA. Plot the result of “the reverse

operating current”.

(4) Reverse the polarity of the diode and repeat the measurement. Plot the result on the same

graph.

(5) Discuss how the behavior of the zener diode is different from rectifier diodes.



Lab 3: Basic DC Power Supply

(1) Form the circuit shown in Fig. 1 on your bread board.

Caution: It is important to observe the proper polarity when working with electrolytic capacitors.

If installed incorrectly, they will fail and may explode.

(2) Use the DMM to measure the average DC load voltage (Vave). Record the value.

(3) Use the oscilloscope to observe and measure the ripple voltage. (Note: The channel 2 input

must be ac coupled to measure the low amplitude ripple voltage.) Draw the ripple waveform

and record its measured peak-lo-peak value (Vp-p).

(4) Change the filter capacitor from 10 μF to 100μF, and repeat Steps 2 and 3. Compare and

explain the results.



Lab 3: Basic DC Power Supply

(1) Modify the circuit as shown in Fig. 2. Adjust the load resistance to 5.6 k Ω.

(2) Measure the DC load voltage and observe the ripple voltage. Record the values.

(3) Change the filter capacitor from 10μF to 100μF, and repeat Steps 2. Compare the results.

(4) With the circuit operating, slowly decrease value of the load resistance. When you first see a

significant decrease in load voltage, power down and measure the value of R L. Record this

value and explain the result.

(5) Explain how the Zener improved the performance of the power supply.



Lab 4: BJT Transistors

(1) Measure and record the accurate value of the 100k Ω resistor.

(2) Construct the circuit shown in Fig. 1 on your bread board. Both supply voltages should be set

initially to 0 V. (If there are no dual variable power supplies available, use the single variable

power supply for VBB, and the voltage source from the analog lab unit for VCC.)

(3) Calculate the value of VR1 that would be generated by a base current of IB = 5μA through R1.

Adjust VBB to obtain the value of VR1 calculated for IB = 5μA.

(4) Adjust VCC so that VCE = 0.5 V. (Or 3 V if using the source from the analogue lab unit.)

Measure and record the value of the current at the collector.

(5) Repeat the step (4) for VCE up to 20 V. Plot the results.

(6) Repeat the step 4)-5) for IB = 10, 20, 40μA.

(7) Explain the results.



Lab 4: BJT Transistors

(1) Construct the circuit shown in Fig. 2.

(2) Connect the input signal to the Ch 1 of the oscilloscope. Connect the output voltage across R L

to the Ch2 of the oscilloscope. Measure and record the peak-to-peak values of the two signals.

Calculate the voltage gain of the amplifier.

(3) Using the basic law of voltage division, we can easily measure the input impedance of this

amplifier- Insert a 2k Ω potentiometer between the signal generator and the input coupling capacitor

C1.

- Connect the oscilloscope as shown in the Figure at the bottom left corner of the sheet.

- Adjust the potentiometer until the signal on Ch2 is exactly half the input value on Ch1.

- Power down and remove only the potentiometer.

- Measure the resistance of the potentiometer. This is equal to the input impedance of the

amplifier.

(4) Restore the circuit to the original configuration. Change RL to 1 k Ω and repeat the step (2)

(5) Restore RL to 100 k Ω, remove the bypass capacitor CB, and repeat the step (2).(6) Explain the results.



Lab 5: FM Wireless MIC kit





Lab 6: Op Amps: Open Loop, Inverting, Non-inverting

(1) Form the circuit shown above on your bread board.

(2) Connect function generator to input and Ch A of scope. Look at output with Ch B. Display

both traces.

- Vary input amplitude, frequency, DC offset and waveform. Observe output.

- Can you see why this circuit is sometimes called a zero crossing detector?

(3) Measure the output Vp-p. What limits the output voltage?

(4) With a 10 Hz, 100mVp-p triangular wave input symmetrical about ground, look foroscillations on the positive and negative transitions at the output. If no oscillations are seen,

remove 0.1㎌ capacitors and look again with the scope. Replace capacitors.



Lab 6: Op Amps: Open Loop, Inverting, Non-inverting


(2) With the input shorted, observe DC change in output voltage as 25K pot is adjusted. Use your

scope and DMM for observations.

Adjust the 25K for 0 volts at the output with the input shorted. Disconnect short.

(3) Connect function generator to input and Ch A of scope. Look at output with Ch B. Display

both traces.

- Vary input amplitude, frequency, DC offset and waveform. Observe output on scope.

- What is the frequency response (high and low -3db points)?(4) With 1KHz, 10Vp-p sine wave in, try loading the output with a 100 Ω resistor.

How was the output affected? What is the maximum observed output current? (Remove 100Ω

resistor when finished.)

- Shunt Rf with 0.01㎌ capacitor. Re-measure frequency response and if it changed, explain why.



Lab 7: Op Amps: Summing, Differential

(1) Form the circuit shown above on your bread board

(2) Connect function generator to Vin1 and Ch A of scope. Look at Vout with Ch B. Display

both traces. Connect Vin2 to a variable DC voltage source (use the 25K pot as a voltage

divider off the +15V and -15V supplies).

- Try combinations of Vin1 amplitude, frequency, offset and waveform along with changes in the

DC voltage on Vin2. Observe output.

- Note that the signals on Vin1 and Vin2 are adding and the sum is inverted. Also note that it is

possible to exceed the input and output linear operating range of the circuit with large input

signal combinations.

(3) What effect will shunting R3 with a 1㎌ capacitor have on the frequency response from Vin1

to Vout? From Vin2 to V out ? Remove capacitor before proceeding.

(4) What effect will a 1N5231B zener have if it is put across R3 with the cathode to the output

side? Try it. Remove zener before proceeding.

(5) Disconnect signal from Vin1. Change R2 to 10MΩ and connect Vin2 to a variable DC

voltage source as in the previous experiment. Observe the output with scope and DMM as you

change Vin2.What is the gain from Vin2 to Vout?

- Adjust output for 0 volts. This is another way to null input offset voltages for amplifiers that do

not have offset pin provisions.

(6) Explain how to add another input, Vin3 with a Vin3 to Vout gain of -13.33.



Lab 7: Op Amps: Summing, Differential


(2) Using your DMM, adjust 25K pot for 0 volts out with Vin1 and Vin2 shorted to ground.

(3) Short Vin1 and Vin2 together and connect to the function generator output. Apply 10Vp-p,

100Hz sine wave with no DC offset and measure Vout with scope. If Vin1 were ideal and all

resistors were exact, what output would you expect?- Account for any difference in the actual Vout vs. ideal. Increase and decrease the frequency and

try other waves to see what happens to Vout.

(4) Build test circuit in Fig. 3 and connect to differential amp. Make Vgen=8Vp-p, 100Hz sine

wave with no DC offset. Calculate voltages at Va, Vb. Measure Vout and explain result. What

is the differential input voltage?

- Increase frequency and note changes to Vout. Try other waveforms and DC offset to see effects.

(5) Could you use your DMM for the above experiments instead of your scope and if so what are

limitations you’d have to watch out for?



Lab 8: Op Amps: Integrator, Differentiator


(2) Connect function generator to Vin and Ch A of scope. Look at Vout with Ch B. Display both

traces. Vary input amplitude, frequency, offset and waveform. Observe output on scope.

- What is the frequency response of this circuit?

(3) Short Vin to ground and remove R2. What happens to Vout and why? What is the polarity of

the input offset voltage? Replace R2 before proceeding.

(4) If Vin is a 2Vp-p, 250Hz square wave with no DC component, what shape and amplitude will

Vout be?

(5) At what low frequency limit does this circuit stop behaving like an integrator?

(6) If Vin were shorted to ground , what would be the worst case DC Vout? Measure the actual

value.



Lab 8: Op Amps: Integrator, Differentiator


(2) R1 and C2 are necessary for stability. Explain why. Short R1 and open C2. See if the circuit

oscillates with Vin open, grounded or with a signal. Restore R1 and C2.

(3) What will be the amplitude and wave shape of Vout with a 1KHz, 1Vp-p triangular wave on

Vin. Confirm your calculation by measuring with a scope.

(4) Try other waveforms and observe output. Does the DC offset on the generator have any

effect on Vout? Why?



Lab 9: Op Amps: Active Filters

Low pass filter:

(1) Calculate the cutoff frequency for the single-pole low-pass filter, f C = 1/ (2π RC ) , shown in

Fig. 1.

(2) Construct the circuit shown in Fig. 1. Adjust the function generator to produce a 1 V p-p sine

wave at one-fourth the value of f C calculated in step (1)

(3) Measure and record the peak-to-peak input and output values in the table below. Use these

values to calculate ACL = vout / vin and ACL(dB) = 20 log ACL.

(4) Change the operating frequency as listed in the table and repeat the measurement.Record the results.

High pass filter:

(5) Modify the circuit in such a way that R1 and C1 are exchanged with each other.

(6) Repeat the steps (1) – (4) for 4 f C , f C , f C /2 and f C /4.



Lab 9: Op Amps: Active Filters

Low pass filter:

(1) Calculate the cutoff frequency for the two-pole low-pass filter,2121

2

1

C C R R f C

π

= , shown

in Fig. 2.

(2) Construct the circuit shown in Fig. 2. Adjust the function generator to produce a 1 V p-p sinewave at one-fourth the value of f C calculated in step (1)

(3) Measure and record the peak-to-peak input and output values in the table below. Use these

values to calculate ACL = vout / vin and ACL(dB) = 20 log ACL.

(4) Change the operating frequency as listed in the table and repeat the measurement.Record the results.

High pass filter:

(5) Modify the circuit in such a way that R1 /R2 and C1 are exchanged with each other.

(6) Repeat the steps (1) – (4) for 4 f C , f C , f C /2 and f C /4.

Documents

Electronic Physics Lab 2011