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Transcript
Exp # (1)
Introduction to OrCAD
‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬
Objectives:
• To Be familiar with the Orcad simulation.
• To be familiar with types of analysis in Orcad program.
• To make analysis to some examples on each analysis.
Equipments:
Computer – Orcad software program.
Introduction to Orcad:
SPICE is a powerful general purpose analog and mixed-mode circuit simulator that is
used to verify circuit designs and to predict the circuit behavior. This is of particular
importance for integrated circuits.
Simulation Program for Integrated Circuits Emphasis.
SPICE can do several types of circuit analyses. Here are the most important ones:
• Non-linear
DC analysis: calculates the DC transfer curve.
• Non-linear
transient and Fourier analysis: calculates the voltage and current
as a function of time when a large signal is applied; Fourier analysis gives the
frequency spectrum.
• Linear AC
Analysis: calculates the output as a function of frequency. A bode
plot is generated.
• Noise
analysis
• Parametric
analysis
• Monte Carlo
Analysis
In addition, PSpice has analog and digital libraries of standard components (such as
NAND, NOR, flip-flops, MUXes, FPGA, PLDs and many more digital components ).
This makes it a useful tool for a wide range of analog and digital applications.
All analyses can be done at different temperatures. The default temperature is 300K.
The circuit can contain the following components:
• Independent
and dependent voltage and current sources
• Resistors
• Capacitors
• Inductors
• Mutual
inductors
• Transmission
lines
• Operational
amplifiers
• Switches
• Diodes
• Bipolar
• MOS
transistors
transistors
• JFET
• MESFET
• Digital
gates
Algorithm of simulating a circuit
The following figure summarizes the different steps involved in simulating a circuit
with Capture and PSpice. We'll describe each of these briefly through a couple of
examples.
Figure 1: Steps involved in simulating a circuit with PSpice.
The values of elements can be specified using scaling factors (upper or lower case):
U or Micro
(= E-6);
T or Tera
(= 1E12);
N or Nano
(=
E-9);
G or Giga (= E9);
P MEG
or Picoor(=
E-12)
Mega
(= E6);
F of Femto
(=
E-15)
K or Kilo (= E3);
M or Milli (= E-3);
2
Types of analysis in Orcad:
1) BIAS Point or DC analysis
1. Draw the circuit shown in figure 2 on the capture window
2.With the schematic open, go to the PSPICE menu and choose NEW
SIMULATION PROFILE.
3. In the Name text box, type a descriptive name, e.g. Bias.
4. From the Inherit From List: select none and click Create.
5. When the Simulation Setting window opens, for the Analyis Type, choose
Bias Point and click OK.
6. Now you are ready to run the simulation: PSPICE/RUN
7. A window will open, letting you know if the simulation was successful. If
there are errors, consult the Simulation Output file.
8. To see the result of the DC bias point simulation, you can open the
Simulation Output file and it will be as shown below.
Figure 2: Results of the Bias simulation displayed on the schematic.
2) Transient Analysis
1. Draw the circuit as shown in figure 3
2. Insert the Vsin source from the library Source. Double click on the source and
make the following changes FREQ = 1000, AMPL = 1, VOFF = 0.
3. Set up the Transient Analysis: go to the PSPICE/NEW SIMULATION
PROFILE.
4. Give it a name (e.g. Transient). When the Simulation Settings window opens,
select "Time Domain (Transient)" Analysis. Enter also the Run Time. Lets make it
5 ms(5 periods since FREQ = 1000). For the Max Step size, you can leave it blank
or enter 10us.
5. Run PSpice.
6.The results is shown in figure 4
Figure 3: the circuit diagram
3
1.0V
0.5V
0V
-0.5V
-1.0V
0s
V(D1:2)
0.5ms
V(V4:+)
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
Time
Figure 4: Results of the transient simulation
3) AC Sweep Analysis:
The AC analysis will apply a sinusoidal voltage whose frequency is swept over a
specified range. The simulation calculates the corresponding voltage and current
amplitude and phases for each frequency. When the input amplitude is set to 1V, then the
output voltage is basically the transfer function. In contrast to a sinusoidal transient
analysis, the AC analysis is not a time domain simulation but rather a simulation of the
sinusoidal steady state of the circuit. When the circuit contains non-linear element such as
diodes and transistors, the elements will be replaced their small-signal models with the
parameter values calculated according to the corresponding biasing point.
1. Create a new project and build the circuit as shown in figure 5
2. For the voltage source use VAC from the Sources library.
3. Make the amplitude of the input source 1V.
4. Create a Simulation Profile. In the Simulation Settings window, select AC
Sweep/Noise.
5. Enter the start and end frequencies and the number of points per decade. For
our example we use 0.1Hz, 10 kHz and 11, respectively.
6. Run the simulation
7. In the Probe window, add the traces for the output voltage.
8. The results is as shown in figure 6
Figure 5
4
600mV
400mV
200mV
0V
100mHz
300mHz
V(R4:2)
1.0Hz
3.0Hz
10Hz
30Hz
100Hz
300Hz
1.0KHz
3.0KHz
10KHz
Frequency
Figure 6
4) DC Sweep Analysis:
The DC sweep is used to draw the voltage transfer characteristic (VTC) between
output and input.
1) we connect the circuit as shown in figure
2) from dc sweep analysis we choose primary
sweep and we put the name of the source V1
and start value (0),end value (12) and
increment (0.1).
3) Then choose secondary sweep and put the
name of the current source I2 and start value
(-4u),end value (12u) and increment (4u).
4) we put the current marker above R2 as shown.
5) The result will be as shown in the figure 8.
Figure 7
Output Current
2.0mA
1.0mA
0A
-1.0mA
0V
1V
2V
3V
4V
5V
6V
-I(R2)
V_V1
Figure 8
5
7V
8V
9V
10V
11V
12V
Home Work
Part one
6) Draw the circuit as shown on capture window with V1= 5v, f=1khz
7) Draw the output voltage across resistor
8) If we connect capacitor (10UF) in parallel with resistor draw the output voltage
D1
9) Make comparison between 2 and 3
10) What is the effect of capacitor on the system
D1N5399
V1
R
1k
Part two
0
1)
2)
3)
4)
5)
Connect the filter as shown on capture window
Make the simulation to AC Sweep
Draw the frequency response of the system
What is the type of the filter
What is the bandwidth of the filter
L1
V1
C1
10m
100u
1v
R1
1k
Part three
0
Draw the characteristic of the JFET (The device number is BF245A) Transistor using
ORCAD Program and draw the circuit schematic related to the characteristic
6
Exp # (2)
BJT Inverter
‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬
Objectives


To be familiar with the operation of BJT Amplifier.
To determine VTC of the inverter.
Theoretical Background
1. Ideal Inverter Digital Gate
The ideal Inverter model is important because it gives a metric by which we can judge
the quality of actual implementation. Its VTC is shown in figure 1.1 and has the
following properties:
Infinite gain in the transition region, and gate threshold located in the middle of the
logic swing, with high and low margins equal to the half of the swing. The input and
output impedance of the ideal gate are infinity and zero, respectively.
2. Dynamic Behavior of Inverter Digital Gate
Figure1.2 illustrates the behavior of the inverter digital gate using BJT
There are three regions for the above voltage transfer characteristic
1. Cut-off region.
2. Forward Active region.
3. Saturation region.
7
BJT Inverter can be best expressed by its voltage transfer characteristic (VTC) or DC
transfer characteristic as shown in figure 1.3. That relates the output voltage to the
input one.
If:
 Vi = Vol, Vo = Voh = Vcc (VTC) or DC transfer characteristic
The transistor is off.
 Vi = Vil
The transistor Begins to turn on.
 Vil < Vi < Vih
The transistor is in forward active region and operates as Amplifier.
 Vi = Voh
The transistor will be deep is saturation, Vo = Vce(sat).
 A measure of sensitivity to noise is called Noise Margin (NM)which can be
expressed by:
Nml = Vil – Vol.
Nmh = Voh – Vih.
 Logic Swing Ls = Voh – Vol
 We can calculate the transition width using the following expression
Tw = Vih - Vil.
 Another point of interest of the VTC is the gate or switching trethold voltage
Vm that defines as Vm = F(Vm).
Vm can also be found graphically at the intersection og the VTC curve
and the line given by Vout = Vin as shown in figure 1.3
 For an AC input, the propagation delay can be defined as:
Tphl: the response from a low to high transition.
8
Tplh: the response from a high
to low transition.
Tp: Overall propagation delay:
Tp = (Tphl + Tplh)/2.
Tr: Rising Time.
Tf: Falling Time.
Procedure
Part A:
1) Write the circuit shown in Figure 1.5:
2) Vary the input Voltage according to the table 1.1
VI
Vo
0.1
0.2
0.3
Vil
1
Vil = ……..
Vih = …….
Vol = …….
Voh = ……
1.5
2
2.5
3
Tw = ……
Nmh = …..
Nml = …...
Ls = ……..
3) Draw the relation between Vo & Vin (Using Drawing paper)
9
3.5
Vih
Part B:
1) Write the circuit shown in figure 1.6:
2) Apply a square wave input (F = 1Hhz, Vp = 5v)
3) Using the Oscilloscope draw Vo&Vin in same paper and same scale.
4) From the graph measure:
Tplh = …………
Tphl = …………
Tp = …………...
Tr = …………....
Tf = ……………
10