Introduction to PSpiceSyafeeza Binti Ahmad Radzi

Computer Engineering Department

FKEKK

Review

Multisim – Digital circuit

PSpice – Analogue circuit (electric / electronic circuit)

PSpice

Same function as MultisimCan be used to design - Digital circuit- Analogue circuit- PCB design- IC designMultisim is used for education purposes while PSpice is widely used in the industry.

What Can You do with PSpice

DC Node AnalysisDC sweeps, component value sweepsSmall signal parametersFrequency response & Bode PlotsTransient ResponseTemperature analysisMonte Carlo Analysis (for component variations)Noise Analysis

LAB 5

4.0 DC NODAL ANALYSIS

Every analysis begins with DC Node calculation. Calculate only DC currents and voltages. Capacitors open circuits.Circuit inductors short circuits.

4.1 BASIC DC NODAL ANALYSIS

DC NODAL ANALYSISCreate Netlist: Analysis Create Netlist.

Simulate the circuit: Analysis Simulate. We will see that the IPROBE and VIEWPOINT parts display the

results of the node voltage analysis. The results of analysis are kept in the output file.

Examine the netlist file: Analysis Examine Netlist. (shows the circuit connection and the number of node)

Examine the output file: Analysis Examine Output. (shows the result of the node voltage analysis)

4.1 BASIC DC NODAL ANALYSIS

VIEWPOINT

IPROBE

The IPROBE and VIEWPOINT parts can be used to display the results of the Nodal Analysis On The Schematic.Or you can click the V and I button to display the voltage and current.

5.0 DC SWEEP ANALYSISTo find all DC voltages and currents of a circuit. The DC Sweep is similar to the node voltage analysis, but adds more flexibility. If we use the DC Sweep, we can simulate the circuit for several different values of voltage / current source in the same simulation.

5.1 BASIC DC SWEEP ANALYSIS

How does Vo vary as V1 is raised from 0 to 25 volts?

DC SWEEP

PROBE: Trace Add. Click V(Vo) : voltage at the node Vo vs V1. We can also display current through any device of the circuit vs V1.

5.3 MAXIMUM POWER TRANSFER

Objective: To analyze what value of Rs in the circuit that will deliver maximum power to RL.

Max Power Theorem: Max power occurs when RL = Rs

Adding parameters

Change RL value to {RL_val}N.B. name is unimportant but { } are mandatoryAdd a PARAM symbol (Draw/Get New Part…/ Param)Set up NAME1 and VALUE1 PARAM values (double-click on the symbol).

Click OK

Set-up Parametric sweep

Setup a Parametric sweep (Analysis/Setup…/DC Sweep) Click OKRun DC sweep analysis

Example: MAXIMUM POWER TRANSFER power absorbed by RL: V(VL)*V(VL)/RL_val vs

RL P=V2/R

RESULT

Result: Max power transfer occurs when RL_val = 1kohm

Max power transfer occurs when RL_val=1kohm

Kirchoff’s Law

Kirchoff’s Current Law = The algebraic sum of the currents entering a node is zero

I1

I2

I3

I1 + I2 = I3

I1 + I2 – I3 = 0

Cont.

Kirchoff’s Voltage Law = The algebraic sum of the voltages around a closed path is zero.

V1 = VR1 +VR2 +VR3V1 – VR1 – VR2 – VR3 = 0

6.1 TASK 1: DC NODAL ANALYSIS

I1I1I2

I3

Loop 13k (I1 - I3) + 1k(I1 – I2) = 12

3k I1 – 3kI3 + 1kI1 – 1kI2 = 12

4kI1 – 1kI2 – 3kI3 = 12 ---(1)

Loop 21k(I2 - I1) + 2kI2 = -12

1kI2 – 1kI1 + 2kI2 = -12

-1kI1 + 3kI2 = -12 ---(2)

Loop 33k(I3 - I1) + 2kI3 =12

3kI3 – 3kI1 + 2kI3 =12

-3kI1 + 5kI3 = 12 ---(3)

Cont.

Solve the equation using Cramer’s Rule. Find the value of I1, I2 and I3. Then, find the DC node voltages for the circuit.

Ax = b4k -1k -3k-1k 3k 0-3k 0 5k

I1

I2

I3

=

12-12 12

PSPICE: AC ANALYSIS

AC Sweep: To find Magnitude and Phase of voltage and

currents plots magnitude versus frequency plots phase versus frequency.

Analysis: Bode Plots, gain and phase plots, and phasor analysis.

Applications: To see the frequency response of an amplifier and a filter.

Source: Vac or Iac.

BODE PLOTSBode Plots Frequency Response

Magnitude vs Frequency

Phase vs Frequency

FilterPassive Filter (has R,L,C components)

Active Filter (has active components e.g: BJT) normally operates as an amplifier.

Types of filter:1. Low Pass Filter2. High Pass Filter3. Band Pass Filter4. Band Stop Filter

AC Analysis versus Transient Analysis

AC SWEEP TRANSIENT ANALYSIS

Source VAC/IAC VSIN/ISIN/pulse etc (time-varying sources)

Analysis Magnitude vs. frequencyPhase vs. frequency(Bode Plot)

Voltage vs. timeCurrent vs. time(Waveform vs. time)

Setup Set point/dec;Start frequency, End Frequency

Set final time; print step

Set-up VAC sourceSet-up VAC*

DC=0used to find initial DC solution

ACMAG=1source p-to-p value during AC analysis

ACPHASE=0reference for phase measurements

Set-up AC analysis and Probe

From Menu Analysis/Setup…

or Toolbar -

Click “AC Sweep” Enter as shown Click “OK”

Application:Measure the f3dB point of v_out using the cursors

In Probe: Trace/Add, DB(V(v_out)) To make cursors active -

select Place one cursor on

nominal 0dB point Move other cursor until “dif”

shows difference of 3dB

Measure the f3dB point of v_out using a goal function

N.B. to see a detailed explanation of this goal function and its parameters, select:

Trace/Goal Functions, LPBW, View The g.f. can also be evaluated from this window (select Eval instead of View)

In Probe:Trace/Eval Goal Function…

Select: LPBW(1,db_level)

Select: V(v_out)

Enter 3 from the keyboard

Click on OK

Filter Design (3dB cutoff) – Example: Low Pass Filter

Amplifier Gain AnalysisA=Vo/VinVin=1VA=VoGain=20 * log10 AGain = 45.7 dBLower 3dB Freq=62.1 HzUpper 3dB Freq=6.9 MHz

Use calculations to prove this simulations!

Transient AnalysisWaveform (voltages or currents) versus time. Pspice will simulate the time response of the circuit.Sources: Vsin, Isin, Vpulse, Ipulse, etc. The duration of simulation depends on the time constants in the circuit. Specify the step size, or time increment, to be used by Pspice.Use probe to view the results graphically. Probe will generate plots of voltage or current versus time.

Transient Analysis Setup

Transient Analysis Setup:Final Time:

Final Time is the length of simulation. F VSIN = 60 Hz T = 1/F = 1/60 s

For 3 cycles simulation: 3T = 3 (1/60) = 50 ms = FINALTIME

Print Step: Every Print Step seconds, the probe will print out the specified values in the output. Choose Print Step = 1ms

No Print Delay: If we want to print data for the last 20ms of simulation: No-Print Delay = 50ms – 20ms

= 30ms PSpice will save and print simulation data after this time.

Step Ceiling: Leave it blank to get the fastest simulation time. PSpice will take the largest value of Step Ceiling allowed for simulation, but the plot maybe

jagged. Reduce Step Ceiling to obtain smoother and nicer plot by divide with some numbers of

points.It will increase simulation time.

Step Ceiling= T/1000 points = (1/60) / 1000

= 0.01667ms

Example: Amplifier Voltage Swing

Monte Carlo AnalysisINTRODUCTION:To assign tolerance values of components.

Example: Resistors have values indicated in color code – and they never change.

In the real world, all resistors have tolerances, which specify how they might vary from their nominal values.

To determine the effects of such tolerance variations, PSpice offers Monte Carlo Analysis.

MONTE CARLO

Used to observe how device tolerances can effect a design.2 types of Analysis: Worst Case: to find maximum and minimum

value of parameter given tolerances. Monte Carlo: to estimate tolerance variation.

Device Model: Uniform Distribution Gaussian Distribution

MODEL: Tolerance - Distribution

Resistor: .MODEL R5pcnt RES(R=1 DEV/UNIFORM 5%) .MODEL R5gauss RES(R=1 DEV/GAUSS 1.25%)

NPN BJT Transistor: .MODEL QBf NPN(Bf=200 DEV/UNIFORM 150) .MODEL Q2N3904B NPN(Is=6.734f DEV/UNIFORM 10%

Xti=3 Eg=1.11)

Capacitor: .MODEL CAP20_80 CAP(C=1.3 DEV/UNIFORM

38.461538%)

Example:Voltage dividerUsing 5% resistor with Gaussian distribution. Find gain, Av=Vo/Vin

By calculations:1) Nominal voltage gain.2) Worst case maximum gain.3) Worst case minimum gain.

By analysis – worst case analysis.

Worst case analysis setup and output file

Monte Carlo

To estimate % tolerance variation that pass specifications-in case max and min value exceed specifications.

Monte Carlo output filef=lV(Vo)-0.5lGain=(Nominal gain)-(deviation)=(0.5)-(0.0202)=0.4798% of nominal = [0.5/0.4798]*100=104.03% upperPass>0.01 [0.5-0.49=0.01]

Monte Carlo – Probe as histogram

histogram

Uniform Distribution

Sigma 0.0102217

Minimum 0.475392

Maximum 0.524402