1. CTU: EE 415 – Advanced Electronics: Lab 3: Curve Tracer 1
Colorado Technical University
EE 415 – Advanced Electronics
Lab 3: Curve Tracer
September 2010
Loren K. Schwappach
ABSTRACT: This lab report was completed as a course requirement to obtain full course credit in EE415,
Advanced Electronics at Colorado Technical University. This report examines the components of a curve tracer by building
upon knowledge gained from previous labs.
If you have any questions or concerns in regards to this laboratory assignment, this laboratory report, the process
used in designing the indicated circuitry, or the final conclusions and recommendations derived, please send an email to
LSchwappach@yahoo.com.
I. INTRODUCTION IV. PROCEDURES / RESULTS
A curve tracer is used to model the current versus This section outlines the procedures required to
voltage characteristics of transistors and other devices. In reproduce this lab and obtain similar results.
this lab assignment a general curve tracer design is attempted
using previous Op-Amp circuit designs. The final design
(curve tracer) is finally tested and the results were verified by A. PART 1 – 1 KHZ OSCILLATOR
the course instructor.
The 1k Hertz oscillator is the first major component
II. OBJECTIVES of the curve tracer. This oscillator is used to drive the rest of
the circuit, specifically a integrator and step generator.
As previously mentioned, this lab assignment built
upon designs created from previous labs, specifically the i. CALCULATIONS:
integrator and oscillator as sources for a transistor curve
tracer. The final curve tracer design included A 1k Hertz Schmitt Trigger Circuit:
oscillator, a step generator, and a reset circuit all designed
and verified using Multisim prior to physical circuit
construction.
III. DESIGN APPROACHES/TRADE-OFFS
Oscillator Circuit:
Hand calculations for the oscillator and integrator
were completed on previous labs. However as noted in
previous labs a few modifications to each design became
necessary to ensure optimal RC combinations. Finally, the
step generator and reset circuit required several hours of
experimentation in Multisim to produce and figure out good
resistor values to use for the reset circuitry.
ii. EQUIPMENT:
 +/- 15 Volts Direct Current (VDC) Power Source
 Signal Generator
 Breadboard
 Three (3) 412k Ohm Resistors
 One (1) 1n Farad Capacitor

2. CTU: EE 415 – Advanced Electronics: Lab 3: Curve Tracer 2
 741 Op-Amp iv. RESULTS:
 Multisim Version 11, by National Instruments As shown by Figure 2 the oscillator correctly
 Oscilloscope produced a 15 Vp signal oscillating at 1k Hertz.
iii. CIRCUIT DIAGRAM:
Figure 2: Multisim Transient Analysis Results of 1k Hertz
oscillator.
Figure 3: Oscilloscope results of 1k Hertz oscillator.
B. PART 2 – 1 KHZ INTEGRATOR
The integrator circuit takes in the 15Vp square wave
produced by the oscillator and outputs a 15Vp triangle wave
for use by the curve tracer.
i. CALCULATIONS:
Figure 1: Multisim 1 KHz Oscillator, designed the same as
the oscillator in lab #2 but using different RC values.
(8)
(9)
(10)
ii. EQUIPMENT:
 +/- 15 Volts Direct Current (VDC) Power Source
 Signal Generator
 Breadboard
 One (1) 226k Ohm Resistor
 One (1) 1k Ohm Resistor

3. CTU: EE 415 – Advanced Electronics: Lab 3: Curve Tracer 3
 One (1) 1n Farad Capacitor
 741 Op-Amp
 Multisim Version 11, by National Instruments
 Oscilloscope
iii. CIRCUIT DIAGRAM:
Figure 5: Multisim transient analysis results of integrator
output.
Figure 6: Oscilloscope results of integrator output (blue)
and oscillator output yellow.
C. PART 3 – STEP GENERATOR AND RESET CIRCUIT
The step generator took in the 1k Hertz oscillator
square wave output and generated a rising step pattern. The
number of steps produced was dependent upon the input
voltage provided to the reset circuit (comparator). The two
diodes (D1 and D2) allowed rectification of the oscillator
Figure 4: Multisim 1 KHz Integrator, designed the same as output and ensured that the step generators output
the Integrator in lab #1 but using different RC values. increased each cycle of the oscillator until finally reset by the
reset circuit.
iv. RESULTS: The reset circuit compared the step generators
output with an externally provided (via voltage divider) bias
As shown by Figure 5 the integrator correctly to allow the resetting of transistor Q2. When transistor Q2 is
produced a 15 Vp signal oscillating at 1k Hertz. The oscillator conducting it is in the reset condition, and provides a path for
and integrator outputs are shown side by side on the current around capacitor C4 (not yet shown). When C4
oscilloscope display Figure 6. discharges the output and input of the step generator
equalize resetting the step generator.
i. CALCULATIONS:
No calculations were required, because the step
generator and reset circuitry was provided by the instructor.
However, modifications to the step generator and
reset circuits were required to component availability
(capacitors). Finally the instructors design was improved by
using variable resistors (potentiometers) in Multisim,

4. CTU: EE 415 – Advanced Electronics: Lab 3: Curve Tracer 4
changing the Reset comparators input voltage and
experimenting with different resistance values. These
experiments led to the final circuit diagram displayed as
Figures 2 and Figure 8.
ii. EQUIPMENT:
 +/- 15 Volts Direct Current (VDC) Power Source
 Signal Generator
 Breadboard
 One (1) 100k Ohm Resistor
 One (1) 87.5k Ohm Resistor
 One (1) 80k Ohm Resistor
 One (1) 30k Ohm Resistor
 One (1) 5k Ohm Resistor
 One (1) 1k Ohm Resistor
 One (1) 1n Farad Capacitor
 Two (2) Diodes (PN: 1N4001)
 Two (2) 741 Op-Amps
 Multisim Version 11, by National Instruments
 Oscilloscope Figure 8: Multisim Reset Circuit.
iii. CIRCUIT DIAGRAM: iv. RESULTS:
.
As shown by Figure 3 the step circuit correctly
produced approximately 5 to 7 steps (nominally 6) before the
reset circuit reset the step generator. Each step occurs at
approximately 1ms (1k Hertz). The reset circuit caused a
reset when the input reset voltage reached an externally
generated reference voltage. The largest influence on the
number of steps created is due to the difference between
capacitors C4 (not yet shown) and C3. Increasing C4 will
significantly increase the number of steps produced.
Figure 7: Multisim Step Generator.
Figure 9: Multisim transient analysis results of step
generator (green) and reset circuit (red).
.

5. CTU: EE 415 – Advanced Electronics: Lab 3: Curve Tracer 5
Figure 10: Oscilloscope results of step generator (yellow)
and reset circuit (blue).
i. CALCULATIONS:
No calculations are required for this step. All that
was required was to put all of the components together.
ii. EQUIPMENT:
All of the previous equipment to include the following
additional equipment:
The (may be modified) resistor values may be amended to
create any shifted / weighted value of Ic vs. Vce curves.
 +/- 15 Volts Direct Current (VDC) Power Source
 Signal Generator
 Large Breadboard
 Two (2) 100k Ohm Resistors (may be modified)
 One (1) 500k Ohm Resistor (may be modified)
 One (1) 15n Farad Capacitor
 Multisim Version 11, by National Instruments
 Oscilloscope

6. CTU: EE 415 – Advanced Electronics: Lab 3: Curve Tracer 6
iii. CIRCUIT DIAGRAM:
.
Figure 11: Final Multisim Circuit Diagram showing finalized curve tracer design.
iv. RESULTS:
Figure 13: Oscilloscope results of curve tracer circuit.
Figure 12: Multisim transient analysis results of oscillator
(purple), Integrator (blue), step generator (green), and reset
(red).

7. CTU: EE 415 – Advanced Electronics: Lab 3: Curve Tracer 7
V. CONCLUSIONS
All component circuitry correctly produced the
desired responses. The oscillator correctly produced a 1k
Hertz output, the integrator correctly integrated that output
into a 1k Hertz triangle wave and the step generator and
reset circuitry correctly produced five steps.
Component availability and selection were
extremely limiting factors in this lab and forced the
redesigning of the step generator and reset circuitry in order
to account for a lack of resistors and small (1pF and 10pF
capacitors) as provided by the instructors reference
document. Further explanation of the Ic vs. Vce curves as a
function of resistors R8, R12, and R13 would have enhanced
Figure 14: Curve tracer results. Ic left, Vce bottom. the final oscilloscope curves (not shown).
REFERENCES
[1] Neamen, D. A., “Microelectronics Circuit Analysis and
rd
Design 3 Edition” John Wiley & Sons, University of New
Mexico, 2007.