circ hw 3

EEE 334Homework 3
* Pictures taken from Sedra, Smith, Carusone, and Gaudet, 8th edition, for academic purposes only.
Copyrights reserved to respective owners.
* Pictures taken from Sedra, Smith, Carusone, and Gaudet, 8th edition, for academic purposes only.
Copyrights reserved to respective owners.
* Pictures taken from Sedra, Smith, Carusone, and Gaudet, 8th edition, for academic purposes only.
Copyrights reserved to respective owners.
* Pictures taken from Sedra, Smith, Carusone, and Gaudet, 8th edition, for academic purposes only.
Copyrights reserved to respective owners.
Please note Example 5.6 is given as a reference for 5.12, D5.13 and need not be done.
Exercises 5.12, D5.13. These exercises are on page 280 – not end of chapter. As the answer for
exercises is given, it is critical to show your work.
* Pictures taken from Sedra, Smith, Carusone, and Gaudet, 8th edition, for academic purposes only.
Copyrights reserved to respective owners.
* Pictures taken from Sedra, Smith, Carusone, and Gaudet, 8th edition, for academic purposes only.
Copyrights reserved to respective owners.
EEE334 Lab #3 – Online
EEE334 Lab#3
PN Junction Diodes and Applications
The objective of this lab is to familiarize the student with basic properties of junction diodes as
well as to provide an overview of some important diode applications.
Sections 3.1-3.3 of the lab involve the study of properties of the PN junction diodes and this
requires knowledge of EXCEL Software. These experiments involve a study of the CurrentVoltage characteristics of PN junction diodes using ADK curve tracer in conjunction with the
ADK oscilloscope and EXCEL to determine the Turn On voltages. Also included are the study
of the DC and small signal (AC) analysis of a diode.
Sections 3.4-3.9 of the lab involve an overview of some important diode applications. These
experiments will enable a student to acquire additional experience in analyzing and evaluating
diode circuits and also to observe typical examples of semiconductor diodes in use. The
applications include wave shaping, such as rectifier, clamper, and limiter (clipper) circuits. A
voltage multiplier circuit is illustrated, as well. For these sections, keep in mind that you will
need to use lab observations and information about these circuits in your book to describe their
function in the Discussion section of the lab report.
This lab contains detailed instructions for equipment set up and LTSpice, and the remaining labs
may not have these detailed instructions.
EEE334 Lab #3 – Online
3.1 Current-Voltage characteristics of PN junction diodes
A curve tracer is an instrument used in analyzing the current-voltage characteristics of a diode or
transistor. This is achieved by varying the voltage or current applied to the device, while
observing the other component. The ADK curve tracer is used in this lab, and it is connected to
the ADK oscilloscope in order to observe and study the
I-V curve of different diodes. The
connections, component placement, settings for the curve tracer and oscilloscope are described
below, and please watch the ‘Lab3’ video which guides you on the use of the ADK kit as a curve
tracer.
You must BUILD the circuit below (Fig. 3.1). BUILD means to construct your circuit on
your breadboard. (Use diodes 1N4001, and 1N914 (or 914b) from your Analog Parts Kit).
Fig. 3.1
Follow the instructions on the ‘Lab 3’ video to set up your ADK for xy plots or current voltage
curves. For each of the diodes 1N4001and 1N914 (or 914b) obtain the current voltage curves.
Sweep the waveform generator from -5V to +3V. Use one channel of the oscilloscope to measure
the voltage across the diode. This will be the x-axis. Use the other channel of the oscilloscope to
EEE334 Lab #3 – Online
measure the voltage across the resistor, which divided by 100 Ohms give the current through the
diode. This voltage will be the y-axis.
POLARITY DESCRIPTIONS ON YOUR DIODES
Fig. 3.2 Diode Configurations
Fig. 3.3a Diode I-V curve
EEE334 Lab #3 – Online
Fig. 3.3b Diode I-V curve (Forward Bias)
1. Ensure a curve resembling Fig. 3.3 above appears on the ADK oscilloscope screen.
a. IMPORTANT, this is an I-V curve, so you must know that the Voltage is on
the X axis and the Current on the Y axis.
2. Ensure the data has been saved.
3. Use Excel, preferably on your laptop to open the data file obtained from the oscilloscope.
a. Before plotting convert the current to its correct units, mA or A. That is,
divide the voltage across the resistor by the resistor value (measure
resistance using the multimeter) to get the current.
4. Plot the data of CH1 (Voltage, X axis) and the converted data of CH2 (Current, Y axis).
a. Use an XY scatter type graph.
b. Label the graph Diode Characterization.
c. Label the axis appropriately including the units i.e. Current in A or mA, Voltage
in V, etc.
5. Determine the value of the Turn on Voltage. There are two ways of doing this. One way
is to find the voltage corresponding to a diode current of ~1mA. The corresponding
voltage is the approximate Turn on or Threshold Voltage of the diode.
Another, more accurate way of determining the Turn on Voltage is to create a Linear
Trend Line for the part of the curve where the current rises exponentially i.e. for the
readings beyond the knee point. Then use the trend-line equation (generated by excel) to
EEE334 Lab #3 – Online
locate the point of intersection of the trend line with the voltage axis. This would give the
approximate Turn on Voltage point. A tutorial for plotting trend-lines has been posted
on Blackboard.
Note: The forward bias I-V curve, the understanding and value with proper units and sign of
the Turn on Voltage are THE OBJECTIVES OF THIS SECTION
3.2 DC analysis of a diode
1. Using the usually assumed Vd for a diode, calculate Vout, and id (the current passing
through the diode) in the circuit shown in Fig. 3.4.
2. Build the Circuit in Figure 3.4 on your Breadboard
a) With your MS8217 multimeter measure the R value (1kΩ resistor)
b) Use the 1N914 (or 914b) diode and set VT to 4V with the ADK waveform
generator.
3. Measure Vout across R using the MS8217 multimeter.
4. Measure id, the current passing in the diode with the MS8217 multimeter. Please see the
video on current measurement with the multimeter.
5. Measure Vd, the voltage drop across diode with the MS8217 multimeter.
D
id
Vout
VT DC
R
Fig. 3.4
EEE334 Lab #3 – Online
6. Simulate the circuit of Figure 3.4 in LTSpice.
a. Use Part D1N914 (or 914b) to simulate the diode. Instantiate the diode. Right
click on the diode and pick a new diode. Choose the 1N914 (or 914b) model. Use
R=1kΩ.
7. Obtain the Current – Voltage characteristic of the diode by doing a DC Sweep of the
LTSpice circuit. Sweep voltage from -1V to +5V.
Hint: To obtain Id vs Vd of the diode, plot the current through the diode. In the plot pane,
click on the horizontal axis (a ruler appears when you hover over it) and enter the
expression of voltage across the diode (V(anode node)-V(cathode node)) in the “Quantity
Plotted”.
8. Once the trace is visible, use the Cursor to obtain the relevant parameters, such as the
Current at 4V in this case.
9. Save a copy of the trace with relevant parameters to be pasted directly onto your lab
report LTSpice results.
10. Use % Error to compare the calculated with the measured and the LTSpice results.
3.3 Small signal (AC) analysis of a diode
1. Calculate Vout assuming Vd = 0.7V, these are the DC voltage drops across the resistor and
the diode respectively in Fig 3.5. Use your calculator. Use VT=4V.
2. According to the Vd assumption from above, calculate Id, the DC current through the diode.
Use your calculator.
3. Build the circuit on your breadboard.
a. Use R=1kΩ. Measure its value first by using the MS8217 multimeter.
b. Use 1N914 (or 914b) diode.
c. Adjust VT to 4V DC on your ADK.
d. Set the ADK-VS, to 1 Vpp sinewave at 1 kHz.
Hint: Use sine wave from AWG1 channel with offset of 4 V and amplitude of 500mV.
4. Use the ADK oscilloscope to obtain:
a. The waveform of Vs and Vout, the AC voltages of the source, and the drop voltage
across the resistor respectively.
EEE334 Lab #3 – Online
i. Pay close attention to waveform offsets, if there is any, record it. What does an
offset represent?
ii. Measure the relevant parameters, such as Vpp and Vrms, of both waveforms.
You can do this with measure /channel 1 or 2 /AC RMS etc…. Add Selected
Measurement.
iii. Save a bmp format copy of the screenshot including the relevant parameters.
iv. Calculate the Vrms for Vs and Vout from the Vpp obtained from the ADK
oscilloscope. Use your Calculator.
v. Are the calculated Vrms’ values equal to the ADK oscilloscope values?
Explain why or why not.
b. Obtain id, the current waveform passing through the diode
Hint: In order to get id, obtain the Vout waveform first, then divide by the actual value
of the resistor. You can do this with control /add mathematical channel etc.
i. Place the relevant parameters, such as Ipp and i(rms), of the waveform on the
screenshot.
ii. Save a bmp format copy of the screenshot including the relevant parameters.
c. Obtain the waveform of Vd, the AC voltage drop across diode
i. Set the oscilloscope to 200mV/div.
ii. Pay close attention to the waveform offset
i. Measure the offset using the Average in the oscilloscope.
ii.
What does this offset represent?
iii. Save a bmp screen shot of Vd and relevant parameter at this resolution.
iv. Place the relevant parameters, such as Vpp and Vrms, of the waveform on the
screenshot.
v. Save a bmp format screenshot including the relevant parameters of your results
at this resolution.
5. Use the ADK multimeter to: (id=diode current, Vd=diode voltage)
a. Measure and record the DC and AC values of Vout.
b.Use the above measurements to determine the DC and rms values of id.
c. Measure and record the DC and rms values of Vd.
EEE334 Lab #3 – Online
id
D
Vout
VT DC
R
VS
AC
Fig. 3.5
6. Simulate the circuit in LTSpice:
a. Use Part D1N914 (or 914b) to simulate the diode. Use VT=4V.
b. Use VSIN for the AC source in your ADK.
c. VSIN settings:
a. VOFF=0, VAMPL=0.5, FREQ=1k
d. For LTSpice results, obtain a Transient Analysis with relevant parameters for Vd,
Vout and Id.
7. Use % Error to compare calculated, lab results and LTSpice results.
3.4 Half-Wave Rectifier (the MS8217 is your Handheld Digital Multimeter)
1. Build the circuit as shown in Fig. 3.6. Adjust ADK-VS to 4 Vpp sine wave at 1 kHz.
RS
D
VL
VS AC
RL
Fig. 3.6 Half-wave rectifier
EEE334 Lab #3 – Online
2. Use RS = RL =1kΩ. Measure their values using the MS8217 multimeter. Use the 1N914
(or 914b) diode in this circuit.
3. Use the ADK Oscilloscope to obtain the input waveform of VS and the output waveform,
VL and relevant parameters.
3.5 Full-Wave Rectifier
Connect the diode bridge rectifier together (four 1N914 (or 914b) diodes + 1 kOhm resistor)
shown in Fig. 3.7.
Fig. 3.7 Diode full-wave rectifier
1. Adjust ADK VS to 4 Vpp Sine Wave with a frequency of 50 Hz and observe the
output waveform.
2. Obtain a screenshot of ONLY the output waveform with relevant parameters. You may
(optional) plot the input alongside the output to observe the full wave rectification effect.
Note: The input to the bridge rectifier must be connected as shown in Fig. 3.7.
Note: You may need to check the output across the resistor without the ground connection
3.6 Peak Detector (Rectifier)
1. Build the circuit as shown in Fig. 3.8. Adjust VS to 4 Vpp sine wave at 1 kHz.
2. Use CL = 0.1uf and RL =100kΩ. Measure their values using the MS8217 meter. Use the
1N914 (or 914b) diode.
EEE334 Lab #3 – Online
3. Using the ADK oscilloscope, obtain the input waveform of VS and the output waveform,
VL and relevant parameters.
4. Simulate the circuit using LTSpice. Obtain the waveform of VS and VL
Note: Use VSIN for the AC source in the LTSpice schematic. VOFF=0, VAMPL=2,
FREQ=1k. Use Part D1N914 (or 914b) to simulate the diode.
5. Are your measured and simulated results matched?
D
VL
VS AC
CL
RL
Fig. 3.8 Peak detector rectifier
3.7 Diode Clamper
1. Build the circuit as shown in Fig. 3.9. Adjust ADK-VS to 6Vpp sine wave at 1kHz and
ADK-VR to 2 Vdc using the 2 waveform generators.
2. Use C = 0.1uf. Measure its value using the MS8217 meter. Use the 1N914 (or 914b)
diode.
C
D
VS
AC
DC
VL
VR
Fig. 3.9 Diode clamper
3. Using the ADK oscilloscope, obtain the input waveform of ADK VS and the output
waveform, VL and relevant parameters.
4. Simulate the circuit using LTSpice. Obtain the waveform of VS and VL.
EEE334 Lab #3 – Online
Note: Use VSIN for the AC source in the LTSpice schematic. VOFF=0, VAMPL=3,
FREQ=1k. Use Part D1N914 (or 914b) to simulate the diode.
5. Are your measured and simulated results matched?
3.8 Diode Limiter (Clipper)
1. Build the circuit as shown in Fig. 3.10. Adjust ADK-VS to 6Vpp Vpp Sine Wave at 1kHz
and ADK-VR to 2 Vdc using the 2 waveform generators.
2. Use R =1kΩ. Measure its value using the MS8217 meter. Use the 1N914 (or 914b) diode.
3. Using ADK oscilloscope, obtain the input waveform of ADK VS and the output
waveform, VL.
4. Also, use the ADK oscilloscope to obtain the Voltage transfer characteristic VL versus
VS.
Set the ADK oscilloscope to XY mode as in lab 3.
R
D
VS
AC
DC
VL
VR
Fig. 3.10 Diode limiter
5. Simulate the circuit using LTSpice and obtain the waveforms of VS, VL and voltage
transfer characteristics (VL versus VS).
Note: Use VSIN for the AC source in the LTspice schematic. VOFF=0, VAMPL=3,
FREQ=1k. Use Part D1N914 (or 914b) to simulate the diode.
6. Are your actual measured results and LTSpice simulated results matched?
EEE334 Lab #3 – Online
3.9 Voltage Multiplier circuit
The circuit in Fig. 3.11 is a voltage multiplier. The circuit operation is similar to that of a full
wave rectifier, when the capacitor voltages are superimposed.
Procedure:
1. Build the circuit as shown in Fig. 3.11. Adjust ADK-VS to 4Vpp Sine Wave at 1kHz.
2. Use C1=C2=47µF, R = 2.2kΩ. Measure its value first using the MS8217 meter. Use the
1N914 (or 914b) diodes.
Note: Pay attention to the capacitors (C1, C2) polarities while connecting them. The
short lead (minus) connects to ground!
3. Use the ADK oscilloscope to obtain ONLY the output waveform, VO, with relevant
parameters.
Fig. 3.11 Voltage multiplier
4. Simulate the circuit using LTSpice. Obtain the waveform of both VS and VO.
Note: Use VSIN for the AC source in the LTspice schematic. VOFF=0, VAMPL=2,
FREQ=1k.
5. Determine the multiplication factor (MF) for measured and simulated results?
EEE334 Lab #3 – Online
(3.1)
Note: The input voltage is an AC voltage, while the output voltage is DC.
6. Are your measured results and simulated results matched?
Post-lab questions:
1. Explain the function of the ADK Curve Tracer in this experiment
Use LTSpice to answer the following post lab questions:
2. In Fig. 3.4 (DC analysis of a diode), what would be Id if:
a. The resistor, R, was shunted (parallel) with a resistor, Rshunt, of equal value (1kΩ).
b. The resistor R was connected with another 1kΩ resistor in series.
c. The diode, D, were shunted (parallel) with a diode, Dshunt (assumed to be
matched).
3. In Fig. 3.5 (Small signal (AC) analysis of a diode), what would happen if the polarity of
the DC voltage source were reversed?
4. What would happen if a capacitor C=47µF were added (in parallel with R) to the diode
circuit shown in Fig. 3.5?
5. Use LTSpice to implement and verify what would happen if the capacitor were increased
ten times in the Peak Detector Rectifier? Explain.
6. Discuss briefly the operation of the voltage multiplier circuit. What would happen if the
capacitors (C1 and C2) were 1µF in the voltage multiplier circuit? Explain.