information on some of the parts in pspice libraries

BSGuru/PS_Parts Jan. 09/2006 1

Information on Some of the Parts in PSpice Libraries

In this documentation, any reference to click is an instruction to click the left mouse button. If a

right click is needed, it will be so stated.

(a) Passive Parts (components) Passive elements are placed horizontally by PSpice in the Schematic window. Current

enters the left terminal, which is marked as node-1 by PSpice. PSpice assumes that the

voltage at node-1 is positive with respect to that at node-2.

The default value of a passive part can be changed using the Display Properties

box, which is opened by double clicking on the part’s value (for instance, 1n (short for 1

nF) for the capacitor).

The initial condition (IC) for the inductor or the capacitor can only be changed by

using the Property Editor, which is opened by double clicking on the part’s symbol. The

Property Editor also allows us to change the part’s value. Don’t forget to click the Apply

button when using the Property Editor. When entering the data, follow the passive sign

convention for the current direction and the polarity of the voltage for each element.

After the simulation is complete, PSpice invokes a post processor, called the Probe,

for sketching various waveforms. It provides a list of Simulation Output Variables. In

this list, one of the entry may be I(R1) for the current through R1. A plot of I(R1) shows a

waveform of the current entering node-1 of R1. Likewise, I(L1) yields a plot of current

entering node-1 of L1. By the same token, a plot of I(V1) will show a waveform for the

current that enters the plus (+) terminal of the voltage source V1. Therefore, it is very

important that you pay attention to the orientation of a component while placing it in the

circuit.

The list of Simulation Output Variables also includes information on power. Power

is computed using passive sign convention. Power dissipated by R1 can be obtained by

plotting W(R1). When a voltage source V1 supplies power to a load, the current exits its

plus (+) terminal. Since PSpice assumes that the current enters the plus (+) terminal of a

part, the graph of W(V1) will show negative power.

Part PSpice Name (Library) PSpice Symbol Passive Sign Convention

Resistor R (ANALOG) R1

1k

Inductor L (ANALOG) L1

10uH

1 2

Capacitor C (ANALOG) C1

1n

(b) Independent dc Sources Independent dc sources are placed vertically by PSpice. Node-1at the top is positive with

respect to node-2 at the bottom. The current enters the source at node-1 and exits at node-2.

This is in accordance with the passive sign convention.


The default value of the source can be changed by using either the Display

Properties box or the Property Editor. Don’t forget to click the Apply button when using

the Property Editor.

Part PSpice Name (Library) PSpice Symbol

DC Voltage Source VDC (SOURCE) V1

0Vdc

DC Current Source IDC (SOURCE) I1

0Adc

(c) Independent ac Sources Independent ac sources are also placed vertically by PSpice with node-1 at the top. These

sources are needed for Phasor Analysis, AC Sweep (sweeping from the lower to upper

frequency with a specified frequency increment), Fourier-Series analysis, and Three-Phase

Circuits.

We advise that the default values should be changed using the Property Editor

because it allows us to change the initial phase angle (ACPHASE) in addition to changing

the dc value and the ac magnitude (ACMAG). Always click on the Apply button prior to

exiting the Property Editor. For these sources, frequency is entered during simulation.


AC Voltage Source VAC (SOURCE) V2

1Vac

0Vdc

AC Current Source IAC (SOURCE) I2

0Adc

1Aac

(d) Independent Sinusoidal Sources Sinusoidal sources are also placed vertically by PSpice with node-1, at the top. These

sources are needed for the transient analysis. While using these sources, make sure to

specify the initial conditions (ICs) for the inductors and capacitors in the circuit. Use the

Property Editor to enter the initial conditions and to change the default values of these

parts. The default value of the phase angle is zero. You can change it to any value. A phase

angle of o120− will be entered as -120 in the PHASE column.


Sinusoidal Voltage Source VOFF: DC offset (V)

VAMPL: Amplitude (V)

FREQ: Frequency (Hz)

VSIN (SOURCE) V3

FREQ =

VAMPL =

VOFF =

Sinusoidal Current Source IOFF: DC offset (A)

IAMPL: Amplitude (A)

FREQ: Frequency (Hz)

ISIN (SOURCE) I3

IOFF =

FREQ =

IAMPL =


(e) Independent Pulsed Sources Pulsed sources are also placed vertically by PSpice with node-1 at the top. These sources

are needed for the transient analysis. While using these sources, make sure to specify the

initial conditions (ICs) for the inductors and capacitors in the circuit. Change the default

values of the parts and enter the initial conditions using the Property Editor.


Pulsed Voltage Source V1: Initial Value (V)

V2: Pulsed Value (V)

TD: Delay time (s)

TR: Rise time (s)

TF: Fall time (s)

PW: Pulse width

PER: Period (s)

VPULSE (SOURCE)

V1

TD =

TF =

PW =

PER =

V1 =

TR =

V2 =

Pulsed Current Source I1: Initial Value (A)

I2: Pulsed Value (A)

TD: Delay time (s)

TR: Rise time (s)

TF: Fall time (s)

PW: Pulse width

PER: Period (s)

IPULSE (SOURCE)

I1

TD =

TF =

PW =

PER =

I1 =

I2 =

TR =

(f) Dependent Sources There are 4 types of dependent sources. The output quantity (voltage or current) is defined

as GAIN times the input quantity (voltage or current). GAIN is entered using the Property

Editor.


Voltage Dependent

Voltage Source

E (ANALOG)

Current Dependent

Current Source

F (ANALOG)

Voltage Dependent

Current Source

G (ANALOG)

Current Dependent

Voltage Source

H (ANALOG)


(g) Reference node (GND)

PSpice requires that every circuit should have at least one reference node (or a

ground node). To place the reference node, click on Ground from Place menu to

open Place Ground window. If the SOURCE library is not part of the libraries in

the Place Ground window, add it by clicking on Add Library. In the new Browse

File window, highlight PSpice and click Open. Now highlight source.olb and click

Open again. The SOURCE library should now be a part of the libraries in Place

Ground window. Now click on 0/SOURCE to place the ground symbol ( 0 ) in

the Place Ground window. Now click OK to place the ground in the Schematic

window.

The Place Ground window can also be opened by clicking on , the 9th

button

from the top on the right-hand side bar menu. Since the ground node is labeled as

zero by PSpice, no other node can be labeled as zero. This is an important

realization when developing your own sub-circuits.

(h) Operational Amplifiers The PSpice libraries contain information on quite a few operational amplifiers such as

LF411, LM111, LM324, uA741, etc. It also has an ideal operational amplifier, listed as

OPAMP, with only three terminals as shown below.


Operational

Amplifier

OPAMP (ANALOG) U1

OPAMP

+

-

OUT

(i) Switches We have used two switches from the PSpice libraries: one that opens at t = 0 and the other

that closes at t = 0. The default value of t = 0 can, however, be changed using Display

Properties box or Property Editor.


Closed switch that

opens at t = 0

Sw_tOpen (EVAL) U1

TOPEN = 0

1 2

Open switch that

closes at t = 0

Sw_tClose (EVAL) U1

TCLOSE = 0

1 2

(j) Transfer Function The library ABM contains a part labeled as LAPLACE. It is nothing but a transfer function

of the generic form given below.


Transfer function LAPLACE (ABM) 1

1 + s

To simulate a transfer function of the type


200s5s

5s102 ++

+,

double click on 1 in the numerator of the PSpice symbol to open the Display Properties

box. Change the value to 5s*10 + and click OK. Now double click on the denominator

s1 + to open the Display Properties box again. Now change the value to

200s*5s*s ++ and click OK.

(k) Print Options We have used two main print options to either sketch the waveforms or save the

information on the phasor voltages and currents in the Output File. If you enter y in each of

the three AC, MAG, and PHASE columns, the Ouput File will have information on

magnitude and phase of each quantity. However, if y is also entered in REAL and IMAG

columns, the real part and the imaginary part will also be part of the Output File.


Ammeter

(Current Printer)

IPRINT (SPECIAL) IPRINT

Voltmeter

(Voltage Printer)

VPRINT2 (SPECAIL)

(l) Magnetically-coupled coils (Transformer) The PSpice part for the coupled coils requires information on the inductance of each coil

and the coefficient of coupling k between the two coils. We can also use this part for an

ideal transformer by making the inductive impedance of each coil much larger than any

other impedance in the circuit. The information on the turns ratio helps us decide the values

of the two inductance in accordance with the following equation:

2

1

2

1

L

La

N

N== or 2

2

1 LaL =


Magnetically-

coupled coils

XFRM_LINEAR

(ANALOG)

TX1

When the part is first placed, it appears as shown above. 1L is the inductance of the

coil on the left and 2L is the inductance of the coil on the right. Use Property Editor

to enter the values of 1L , 2L , and k. Unfortunately, PSpice does not display the

values of 1L , 2L , and k on the schematic. As a helpful aid, you can type these

values yourself using the Text option from Place menu.

(m) Many More Parts

The parts we have listed above form a very small subset of all the parts that are

available in the PSpice libraries. Scan the part’s list, examine each part, and


understand its properties prior to using it. The more you use the PSpice program,

the more proficient you become in using the relevant parts.

The simulation is a tool that must be used very carefully and wisely.

You should be able to analyze the circuit theoretically and predict what sort of

information you will be expecting from the simulation. If you cannot predict the

outcome, the simulation is a waste of time because you will not know if you made

any mistake while entering the data especially the initial conditions.

(n) Suffixes used in PSpice

F (f) P (p) N (n) U (u) M (m) K (k) MEG (meg) G (g) T (t)

femto pico nano micro milli kilo mega giga tera

10-15

10-12

10-9

10-6

10-3

103 10

6 10

9 10

12

Suffixes are case insensitive. A capacitance 2F means a capacitance of 15102 −× farads and

not 1 farad. Likewise, a resistance of 10M is 10 milli-ohms and not 10 mega-ohms.

(o) Bipolar Junction Parameters and their default values

Parameter Description

BF Forward current gain (β )

CJE Base-emitter depletion capacitance

CJC Base-collector depletion capacitance

VAR Reverse Early voltage

VAF Forward Early voltage

BR Reverse beta

NR Reverse emission coefficient

NF Forward emission coefficient

(p) MOSFET Parameters and their default values


VTO Threshold voltage

KP Conductance parameter

LEVEL choose zero for ideal

CBD Drain-to-substrate capacitance

CBS Source-to-substrate capacitance

TOX Oxide-layer thickness


(q) Diode Parameters and their default values


IS Saturation Current

CJO Junction capacitance at VD = 0

VJ Junction voltage

BV Reverse-breakdown voltage

IBV Current at VD = BV

RS Series Ohmic resistance

N Emission coefficient (ideality factor)


(r) Editing/Verifying Parameters in the PSpice Model

It is important to know what values are being used by PSpice in modeling a

component (part). For example, what is the reverse breakdown voltage of a diode,

say D1N4002/EVAL (D is the PSpice designation for the diode. The actual diode

part-number is 1N4002. Its parameters are stored in the EVAL library of PSplice).

Likewise what is the value of β used by the PSpice model for say an npn transistor

(say Q2N3904/EVAL)? Q is the PSpice designation for all bipolar-junction

transistors. 2N3904 is the npn transistor and its parameters are stored in the EVAL

library of PSpice.

To find out the values of the parameters used by PSpice, highlight the component

by left-clicking on it. Once the component is highlighted, it will be surrounded in a

dashed purple box. Right-click within the dashed box to open up a window with

many options. Choose “Edit PSpice Model” by left clicking on it. PSpice Model

Editor will show the default values. Make the necessary changes. For example, to

change the forward current gain β , check for the default value of BF in the list of

parameters and change. Once you made the change, do not forget to save the

change.

information on some of the parts in pspice libraries

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