Name: Daniel Bernard
Team Members: Benjamen Strobel and Jack Ladwig
ECE 2212
Lab #05 Additional Diode Circuits and Applications
Due: March 8, 2012
Lab Coordinator: Stan Burns
Lab TA: Sukriti Subedi
Abstract:
This lab covers the study of double-diode clipping; in time domain and transfer characteristics, voltage
doublers; in time domain and transfer characteristics, and AND, OR, and precision rectifiers in both time
domain and transfer characteristics. Additionally covers junction capacitance measurements based on the
reverse bias voltage, 𝑉𝑅 . The lab details the usage of diodes in limiting input transient voltage so that the
integrated circuit is not damaged. Through the circuits provided, an understanding of Boolean logic can be
surmised and replicated through simple diode circuits. The application of these circuits can exemplify electronic
tuning for communication systems.
Introduction:
This lab covers the study of double-diode clipping; in time domain and transfer characteristics, voltage
doublers; in time domain and transfer characteristics, and AND, OR, and precision rectifiers in both time
domain and transfer characteristics.
Background:
Information required for this lab consists of a basic understanding of nodal analysis, mesh analysis, and
Boolean logic. Using that in conjunction with an understanding of diode analysis and initial conditions/designs
for the 1N4001 and 1N4002 diodes, simulation and synthesization of the circuits used in this lab can be
completed.
Procedure:
Double-Diode Clipper:
Using the circuit diagram, Figure 1, set 𝑉𝑠 (𝑡) = 7 sin(2𝜋100𝑡),
adjusting the amplitude and observing its effect on 𝑉0 (𝑡).
Voltage Doubler:
Using the circuit diagram, Figure 2, use the same frequency
signal as before, but adjust the load resistor between 100𝑘Ω and 1𝑘Ω.
AND/OR gates:
Using the circuit diagrams, Figures 3 and 4, construct
the logic AND and OR gates. Apply a signal waveform that
allows you to see the characteristics of the circuits.
Precision Rectification:
Using the circuit diagrams, Figures 5a and 5b, measure
transfer characteristics and compare the results between the
two circuits.
Junction Capacitance Values:
Using the circuit diagrams, Figures 6a and 6b,
measure corner frequency, 𝑓𝑐 , and make proper
calculations for junction capacitance with respect to
reverse bias voltage, 𝐶𝑗 (𝑉𝑅 ). Include estimations of
capacitance from the wiring in the system, and the coaxial
lead cables.
Measurements and Analysis of Results:
Double-Diode Clipper:
Adjusting the amplitude of the 𝑉𝑠 (𝑡)adjusted the level of
clipping for either the positive or negative clipping of the output
wave as shown in the graphs below. 𝑉1 must be simulated with a
negative voltage.
Circuit 1, V1=-1, V2=1,
Ampl Vs =14
Circuit 1, V1=-1, V2=1, Ampl
Vs =7
V1=2, V2=2, Neg Vout clipping=
2.7, Pos Vout clipping= 2.5
Circuit 1, V1=-2, V2=2, Ampl Vs
=7
Circuit 1, V1=-2, V2=1, Ampl Vs
=7
Voltage Doubler:
The circuit is called a voltage doubler occasionally, because if a
high enough resistance is used, then the output voltage is higher than the input voltage.
R=10
R=75
V1=1, V2=1, Neg Vout clipping=
1.7, Pos Vout clipping= 1.5
V1=0, V2=1, Neg Vout clipping= 1.7,
Pos Vout clipping= .6
Circuit 1, V1=-1, V2=2, Ampl
Vs =7
R=2k\hpK
V1=0, V2=0, Neg Vout
clipping= .6, Pos Vout clipping= .6
R=1
R=30
R=100
V1=1, V2=0, Neg Vout clipping= .6,
Pos Vout clipping= 1.5
R (k)
1
2
10
30
75
100
Ripple Voltage (V)
3
3.5
3.5
2.5
1.5
1
AND/OR gates:
AND gate:
Time on Graph
V4
V5
Logic Level
V0
0-.1
0
0
0
0.7
.1-.2
0
1
0
0.7
.2-.3
1
0
0
0.7
.3-.4
1
1
1
5
The graphs from the oscilloscope show the input signal, and the output
logical zero and one sequentially.
The simulation matched the created circuit.
Additionally, adding the 1𝑘Ω resistor did not appear to affect the output
of the system.
OR gate
Time on Graph
V4
V5
Logic Level
V0
0-.1
0
0
0
0
.1-.2
0
1
1
4.3
.2-.3
1
0
1
4.3
.3-.4
1
1
1
4.3
Precision Rectification:
Transfer Characteristics of
Figure 5A
Transfer Characteristics of
Figure 5B
As you can see from both the oscilloscope readings, and the PSpice transient analysis, the signal goes from being somewhat inexact, to
being very crisp and linear, hence ‘precision rectification’.
Junction Capacitance Values:
Characteristics of Figure
6A
Characteristics of Figure
6B
Oscilloscope measurements are listed as 1𝑀Ω resistance, and we were able to calculate 73𝑝𝐹 of capacitance. Using that, and an
estimation of 30𝑝𝐹/𝑓𝑜𝑜𝑡 for the capacitance of the coaxial lead cables, we were able to adjust our PSpice simulation to be more
accurate. With a 4𝑉 DC offset, the given information for the diodes provided that they would each have a junction capacitance of
15𝑝𝐹. From this, we could calculate corner frequency to be 17.5𝑘𝐻𝑧, and properly test our simulation using the oscilloscope.
Summary and Conclusion:
This lab gave an understanding of how diodes can be used in RC circuits to create different levels of clipping, which can be
used to protect a circuit from being overloaded, and how they can be used to create a more clean and linear transfer characteristic.
From the diode OR and AND gate that was created, we were able to determine how create basic logic gates, and create circuits that
have a function beyond simple waveform output. There was some difficulty in simulating the waveform in PSpice for the logic gates,
as we are unable to have voltage changes at exact points, and so there are some jumps in the transient analysis. We also saw how
diodes could be used to create a voltage doubler, which depending on the resistor values used, could be used simply to convert AC to
DC.