1

LIST OF EXPERIMENTS

1. Pspice simulation of transient response of RLC circuit.

A) response of pulse input B) response of step input C) response of sinusoidal input

3

2. Analysis of three phase circuit representing the generator transmission line and load. Plot three phase currents and neutral current using pspice

9

3. Pspice simulation of single phase full converter using RL&E load and single phase ac voltage controller using RL&E load

19

4. Pspice simulation of resonant pulse commutation circuit & buck chopper.

22

5. Pspice simulation of single phase inverter with pwm control

24

6. Plotting root locus, bode plot & nyquist plots for the transfer functions of the system upto fifth order using mat lab

27

7. Transfer function analysis of any given system upto third order using simulink

28

8. Power flow solution and transient stability evaluation of power system using MATLAB

29

9. Step response of an RLC circuit by parametric analysis using pspice

30

10. Pspice simulation of op-amp based integrator and differentiator.

35

11. Pspice simulation of single phase cycloconverter 37 12. Plotting the JFET characteristics using pspice 38

2

LIST OF EXPERIMENTS: 1. Pspice simulation of transient response of RLC circuit.

a) Response of pulse input b) Response of step input c) Response of sinusoidal input

2. Analysis of three phase circuit representing the generator transmission line and load. Plot three phase currents and neutral current using Pspice 3. Pspice simulation of single phase full converter using RL&E load and single phase ac voltage controller using RL&E load. 4. Pspice simulation of resonant pulse commutation circuit & buck chopper. 5. Pspice simulation of single phase inverter with pwm control. 6. Plotting root locus, bode plot &nyquist plots for the transfer functions of the system upto fifth order using MAT LAB 7. Transfer function analysis of any given system upto third order using simulink 8. Power flow solution and transient stability evaluation of power system using MATLAB Additional experiments: 9. Step response of an RLC circuit by parametric analysis using Pspice. 10. Pspice simulation of op-amp based integrator and differentiator.

Additional experiments (outside the syllabus) 11. Pspice simulation of single phase cycloconverter 12. Plotting the JFET characteristics using Pspice

3

1. TRANSIENT RESPONSE OF RLC CIRCUIT .

AIM : Using PSPICE calculate and plot the transient response of an RLC circuit from 0-

400µs with a time increment of 1µs. Plot V (3) and I(R) for the following inputs (voltage across capacitor and current through resistor):- 1. Pulse input 2. Step input 3. Sinusoidal input

CIRCUIT DIAGRAM:

R

2ohm

R

2ohm

L

50uH

V1

C

10UF

L

50uH

L

50uH

C

10UF

C

10UF

R

2ohm

V1

V1

4

INPUTSOURCES

PULSE INPUT

1NS

200 µs

-220V

220V

100 µs

t

100 200 µs -220V

220V

V

5

STEP INPUT

SINUSOIDAL SOURCE

t(ms)

0.1 0.2 0

10V

t (ms)

1MS 1NS 0

1V

V

t (ms)

1MS 1NS 0

1V

V

0

1V

V

t

6

PULSE SOURCE:- The waveform and parameters of a pulse waveform are shown below .the symbol of a pulse source is PULSE and the general form is VNAME POSITIVENODE NEGATIVENODE PULSE (V1 V2 TD TR TF PW PER)

Where V1&V2 ARE initial and final voltages (volts) TD is delay time (sec) TR is rise time (sec) TF is fall time (sec) PW is pulse width (sec) PER is period (sec) EX: - VS 1 0 PULSE (1 5 1NS 10NS 10NS 50NS 100NS)

PER

TD TR

V2

TF

PW

7

PIECEWISE LINEAR SOURCE :- A point in a waveform can be described by (Ti Vi) OR (Ti Ii) And every pair of values specifies the source value at time ti. The voltage at time between the intermediate points is determined by pspice by using linear interpolation. The symbol of piecewise linear source is PWL VNAME POSNODE NEGNODE PWL (T1 V1 T2 V2……..TN VN) Where Ti & Vi are time and voltage at any point “i” in seconds and volts

EX:- VS 1 0 PWL(0 0 5US 3V 10US 3V 15US 6V 40US 6V 45US 2V 60US 2V 65US 0) SINUSOIDAL SOURCE:- The symbol of sinusoidal source is SIN VNAME POSNODE NEGNODE SIN (V0 VA FREQ TD ALP THETA)

V3

V2 V1

V4

V5 V6

V7

T1 5 µs

T2 10 µs

T3 15 µs

T4 40 µs

T5 45 µs

T6 60 µs

T7 65 µs

t (µs)

6V

3V

0

V

8

WHERE V0 is offset voltage (volts) VA is peak voltage (volts) FREQ is frequency (Hz) TD is delay time (sec) ALPHA is damping factor (1/sec) THETA is phase delay (degrees) EX:- VS 1 0 SIN (0 160 50) for constant magnitude SIN source VO=0 ALPHA=0 TD=0 VS 1 0 SIN (0 160 60 10US 1E5 120) for exponentially decaying SIN source.

Vo

Va

9

2 .GENERATOR, TRANSMISSION LINE AND LOAD AIM:

Use PSPICE to calculate and plot the instantaneous currents IA, IB, IC and IN and total input power PIN from 0 to 50msec with a time increment of 5µs. Also calculate RMS magnitudes and phase angles of currents IA, IB, IC and IN.

CIRCUIT DIAGRAM:

INDEPENDENT A.C. SOURCE:- The statements for a voltage and current source have the following general forms respectively. VNAME POSNODE NEGNODE AC MAGVALUE PHASEVALUE INAME POSNODE NEGNODE AC MAGVALUE PHASEVALUE The magnitude value is the peak value of sinusoidal voltage and the phase is in degrees EX:-

R3

10ohm

RC

0.5ohm

V11Vac0Vdc

RX

1ohm

V2

1Vac0Vdc

C1

150uf

L1

120mh

R1

5ohm

RZ

1ohm

V3

1Vac0Vdc

R2

10ohm

RY

1ohm

RA

0.5ohm

RB

0.5ohm

10

V1 5 6 AC 120V 120DEG SINUSOIDAL SOURCE:- The symbol of sinusoidal source is SIN VNAME POSNODE NEGNODE SIN (V0 VA FREQ TD ALP THETA)

Where V0 is offset voltage (volts) VA is peak voltage (volts) FREQ is frequency (Hz) TD is delay time (sec) ALPHA is damping factor (1/sec) THETA is phase delay (degrees)

V=V0+VAe-∞ (t-td) SIN (2πf (t-td)-Θ) EX:- VS 1 0 SIN(0 160 50) for constant magnitude SIN source VO=0 ALPHA=0 AND TD=0 VIN 1 0 SIN (0 160 60 10US 1E5 120) for exponentially decaying SIN source.

Vo

Va

11

A.C.ANALYSIS:- The a.c. analysis calculates the frequency response of a circuit over a range of frequencies. The command for performing frequency response takes one of the following general forms .AC LIN NP FSTART FSTOP .AC OCT NP FSTART FSTOP .AC DEC NP FSTART FSTOP NP is the number of points in a frequency sweep FSTART is the starting frequency and FSTOP is the ending frequency LIN (LINEAR SWEEP) – The frequency is swept linearly from the starting to ending Frequency and NP becomes the total number of points in the sweep. LIN sweep is used if the frequency range is narrow. OCT (SWEEP BY OCTAVE) – The frequency is swept logarithmically by octave and NP becomes number of points per octave. It is used if the frequency range is wide. DEC (SWEEP BY DECADE) – The frequency is swept logarithmically by decade and NP becomes number of points per octave. It is used if the frequency range is widest. EX: - .AC LIN 10 50HZ 2000HZ OUTPUT VARIABLES :- In ac analysis the output variables are sinusoidal quantities and are represented by complex numbers. An output variable can have magnitude and phase. M- Peak magnitude DB – peak magnitude in decibels’ P – Phase in radians R – real part I – imaginary part EX:- VM (5) – magnitude of voltage at node 5 W.R.T. ground VM (4, 2) – magnitude of voltage at node 4 W.R.T. node 2 IR (VIN) – real part of current through source VIN.

12

TRANSIENT ANALYSIS : Transient analysis calculates the time response of a circuit and it can be performed by the “.TRAN “command which has one of the following general forms. .TRAN TSTEP TSTOP EX:- .TRAN 5US 2MS If we want the initial conditions while performing transient analysis. .TRAN TSTEP TSTOP [TSTART TMAX] [UIC] EX:- .TRAN 5US 1MS 200MS 0.1NS UIC

Where

TSTEP is the printing increment

TSTOP is the final time

TMAX is the maximum size of internal time step

The transient analysis always starts at time=0, but it is possible to suppress the printing of

the output for a time of start

TSTART - initial time at which the transient response is printed

UIC - use initial conditions

These initial conditions can be inductor initial current or capacitor initial voltage which are

described while describing inductance and capacitor

OUTPUT COMMANDS: -

The output commands are

.PRINT TRAN OUTPUT VARIABLES

.PLOT TRAN OUTPUT VARIABLES

.PROBE

.PRINT AND .PLOT prints the output into the output file

.PROBE gives graphical output.

OUTPUT VARIABLES :-

V (2, 3) – voltage of node 2 W.R.T. TO node 3

I (L) – current through inductor L

13

SPICE THYRISTOR MODEL

If a thyristor is operated from an ac source, it should exhibit the following characteristics : 1) It should switch to on state with the application of small positive gate voltage

provided that the anode cathode voltage is positive. 2) It should remain in on state as long as anode current flows. 3) It should switch to off state when the anode current goes through zero towards

negative direction Switching action of the thyristor is modeled by a voltage controlled switch and a polynomial current source.

SWITCH: Pspice allows simulation of special kind of switch whose resistance varies continuously depending on voltage and current

ON STATE-RON OFF STATE-ROFF

There are two types of switches 1) Voltage controlled switch 2) Current controlled switch VOLTAGE CONTROLLED SWITCH: Syntax for voltage controlled switch is S<NAME> N+ N- NC+ NC- SNAME WHERE N+, N- are positive and negative nodes of the switch, current flows from N+ TO N- NC+, NC- are positive and negative nodes of the controlling voltage

N+

S

N-

N+

Ron

N-

N+

Roff

N-

14

EX: S1 6 5 4 0 SMOD .MODEL SMOD VSWITCH (RON=0.5 ROFF=10E+6 VON=0.7 VOFF=0.0) DEFAULT VON CONTROL VOLTAGE FOR ON STATE 1.0 VOFF CONTROL VOLTAGE FOR OFF STATE 0.0 RON ON RESISTANCE 1.0 ROFF OFF RESISTANCE 10E+6 CURRENT CONTROLLED SWITCH Syntax for current controlled switch is W<NAME> N+ N- VN WNAME WHERE N +, N- are positive and negative nodes of the switch, current flows from N+ TO N-. VN is the voltage source through which controlling current flows

N+

S1

N-

N+

W1

N-

NC+

R

NC-

NC+

R

NC-

15

EX: W1 6 5 VN RELAY .MODEL RELAY ISWITCH (RON=0.5 ROFF=10E+6 ION=0.07 IOFF= 0.0) DEFAULT ION CONTROL CURRENT FOR ON STATE 1E-3 IOFF CONTROL CURRENT FOR OFF STATE 0.0 RON ON RESISTANCE 1.0 ROFF OFF RESISTANCE 10E+6 POLYNOMIAL SOURCES : There are four types of dependent sources (VCVS, VCCS, CCCS, and CCVS) And they can have either a fixed value or polynomial expression. Symbol for polynomial are non linear source is POLY (N) Where N is the number of dimensions of the polynomial, by default N=1. SYNTAX:- POLY (N) <CONTROLLING NODES> <COEFFICIENT VALUES> The output of controlling sources can be voltage or currents. For voltage controlled sources the number of controlling nodes must be twice the number of dimensions. For current controlled sources number of controlling sources must be equal to number of dimensions. Number of dimensions and coefficients are arbitrary. EX: VOLTAGE DEPENDENT VOLTAGE SOURCE

NC3+

NC2-

-

NC3-

Y+

NC1-

-

+

-A

NC1+

+C

+

N+

B

NC2+

-

16

DEPENDENT SOURCES ARE DEPENDED ON THREE VARIABLES A,B,C Y = f(A,B,C) IF N=1 i.e. ONLY ONE CONTROLLING SOURCE Y = P0 + P1 A + P2 A

2 + ……………………..+ PN AN

SYNTAX:- POLY NC1+ NC1- P0 P1 P2…………….PN IF N=2 Y=P0 + P1A + P2B + P3A

2 + P4 AB + P5 B2 + P6 A

3 + P7A2B+ …………….

SYNTAX: POLY (2) NC1+ NC1- NC2+ NC2- P0 P1 P2………PN

EX:

1) Y = 2V(10) POLY 10 0 2

2) Y =V(3) + 2V(5) + 3V(10) +4[V(3)]2 POLY (3) 3 0 5 0 10 0 1 2 3 4

3) SIMILARLY IF I(VN) AND I(VX) ARE CONTROLLING CURRENTS THEN Y= I (VN) +2I (VX) +3I [(VN)] 2+4[I (VN)*I (VX)] POLY (2) VN VX 1 2 3 4

THYRISTOR CIRCUIT:

k

1

6

S1

3

RG

2

ADT

VS

GCathode

RTF1=50Ig+11Ia

CT

4

K

1

AnodeA

R

VY5

OV

+

VX

-

2

7

Vg

GateG

OV

17

TURN ON PROCESS: 1. For a positive gate voltage vg between nodes 3 and 2 gate current

Ig=I (Vg) =Vg/Rg 2. The gate current Ig activates the current controlled current source F1 and

produces a current of value Fg = P1 Ig = P1I (Vx) such that F1= Fg+Fa. 3. The current source Fg produces a rapidly rising voltage VR across resistance rt. 4. As the voltage vr increases above zero, the resistance Rs of voltage controlled

switch s1 decreases from Roff to Ron. 5. As the resistance of switch S1 decreases the anode current Ia=I(Vy)

Increases, provided anode cathode voltages are positive. This increasing anode current ia produces a current Fa=P2 Ia =P2 I (Vy) This again results in an increased value of voltage VR.

6. This produces a regenerative condition with the switch rapidly being driven into low resistance i.e on state. The switch remains on even if the gate voltage vg is removed.

7. The anode current Ia continues to flow as long as it is positive and switch remains in on state.

TURN OFF PROCESS: Ig = 0;Fg = 0 F1 = Fg +Fa 1. As anode current Ia goes negative, current F1 reverses provided gate voltage Vg

IS not present. 2. With –VE F1 capacitor Ct dischargers through current source F1 and resistance

Rt. 3. With fall of voltage Vr to a low value, resistance of the switch S1 INCREASES

from RON TO ROFF. 4. This again a regenerative condition with the switch resistance being driven

rapidly to Roff asVR becomes zero.

18

DIODE PARAMETERS SWITCH PARAMETERS Is = 2.2E -15 RON = 0.0125 BV=1800V ROFF=10E+5

TT=0 VON=0.5V&VOFF=0V SYNTAX FOR DIODE D<NAME> ANODE CATHODE MODELNAME .MODEL MODELNAME D(DIODEPARAMETERS) SYNTAX FOR TRANSISTOR Q<NAME> COLLECTOR BASE EMITTER MODELNAME .MODEL MODELNAME NPN(TRANSISTOR PARAMETERS) .MODEL MODELNAME PNP(TRANSISTOR PARAMETERS) SYNTAX FOR THYRISTOR XT<NAME> ANODE CATHODE GATE CATHODE SUBCIRCUITNAME EX:- XT1 1 2 6 2 SCR TO INCLUDE THAT SUB CIRCUIT IN THE MAIN PROGRAM .INC SCR.CIR BEFORE DEFINING THYRISTOR SYNTAX IN MAIN PROGRAM. HOW TO WRITE A SUB CIRCUIT: .SUBCKT NAME ANODE CATHODE GATE CATHODE ----------------------- -------------------- ----------------------- .ENDS NAME In between .SUBCKT AND .ENDS THYRISTOR sub circuit model circuit elements should be defined.

19

3.SINGLE PHASE FULL CONVERTER .

AIM:

A single phase full converter uses delay angle control and is supplied from 120V, 60 Hz supply. Use PSPICE to plot the output voltage and the load current of the single phase full converter with an R L E load

CIRCUIT DIAGRAM:

PULSE INPUTS

TW=100µsec T=16.67msec --------- Tr=Tf=1nsec --------------------------- Take α1=600 , α2=1800+α1

V3

FREQ = 60HZ

VAMPL = 120V

VOFF = 0V

T32N1595

VX

0Vdc

C

100UF

VY

0Vdc

RX

0.1OHM

T22N1595

R

10OHM

T42N1595

L

20mH

T12N1595

Vg1,Vg2 Vg3,Vg4

0v 0v

10v 10v

t 1 or α1 T t t

T t 2or α2=180+α1

t1

20

3. SINGLE PHASE AC VOLTAGE CONTROLLER.

AIM : A single phase AC voltage controller is supplied from 120V (rms), 60Hz. Load is

R=2.5Ω, L=6.5 mH. Delay angle α = 90o . Use PSPICE to plot the output voltage and the load current.

CIRCUIT DIAGRAM:

PULSE INPUTS

Vg2

TW=100µsec T=16.67msec Tr=Tf=1nsec --------- --------------------------

L6.5mH

VX0Vdc

VS

RS

750ohm

CS

O.1UF

R2.5OHM

T22N1595

T1

2N1595

0v 0v

10v 10v

t 1 T t t

T t 2

Vg1

21

4. BUCK CHOPPER. AIM :

A Buck chopper is supplied with input voltage Vs=110v. The chopping frequency f =20KHz. Use PSPICE to verify the results by plotting the instantaneous voltage Vc , and instantaneous load current il

CIRCUIT DIAGRAM:

GATE VOLTAGE TRANSISTOR PARAMETERS:- IS=6.734F BR=0.7371 TR=239.5N BF=416.4 CJC=3.638P TF=301.2P CJE=4.493P DIODE PARAMETERS:- IS=2.2E-15 BV=1800V TT=0;

Dm

Vy

0Vdc

Ce

8.33uf

Le

681.82uH

S

Vg

RB

250ohm

VS

110V

Vx0Vdc

L

40.91uH

R

3ohm

50µsec 27.28µsec 0

20v

Vg

t

22

4. RESONANT PULSE COMMUTATION . AIM:

The circuit parameters of resonant pulse commutation circuit is supplied with voltage Vs=200V, commutating capacitor C=31.2µf, commutating inductance = 6.4µH, load resistance Rm=0.5 Ω and load inductance Lm=5mH, Use PSPICE to plot (a) capacitor voltage, (b) capacitor current and (c) load current. The switching frequencies fc=1 KHz and on-time of the thyristor T1 = 40%.

CIRCUIT DIAGRAM:

Lm

5mH

T3

Vy

0Vdc

Rg3

10Mohm

C

31.2uf

Rg1

10Mohm

Rg2

10Mohm

S

Vs

T1

S

Vg3

Rm

0.5ohm

Dm

T2

Rs

750ohm

L

6.4uH

D1

Cs

0.1uf

S

Vg2

Vx

0Vdc

S

Vg1

23

PULSE INPUTS Vg1 Vg2 Vg3 DCSPICE THYRISTOR MODEL:-

DIODE PARAMETERS:- SWITCH PARAMETERS:- IS=1E-25 RON=0.1,ROFF=10E+6 BV=1000V VON=10V,VOFF=5V .SUBCKT DCSCR Anode Cathode Gate Ref ------------------------ ------------------------- .ENDS DCSCR

CATHODE

5

ANODE

KST

GATE

Rg

2

4

1

3

3

2

ADT

1

Vg

t

t

t

1ms

1ms

1ms

100v

100v

100v

0.4msec

0.4msec

0.2msec

24

5.SINGLE PHASE INVERTER WITH PWM CONTROL . AIM :

The 1-ф Inverter uses the PWM control with pulses per half-cycle. The dc supply voltage is Vs=100. The modulation index M is 0.6. The output frequency is fo =60Hz. The load is resistive R=2.5Ω. Use PSPICE (a) to plot the output voltage Vo,

CIRCUIT DIAGRAM:-

Q4

Vg3

D4D2

L1

10uH

Q2

D1

Vg1

Vg4

Rg1

100

V3

0Vdc

Vx

0Vdc

Rg4

1k

Vg2

Rg2

1k

Q1Q3

Vs

100v

Rg3

1k D3

R1

2.5

2Mohm

Rc3Rc2Vc1

S S

2Mohm

0

S Vc3

2Mohm

Rc1

17

Vc2

1615

25

OPAMP COMPARATOR AS PWM GENERATOR:

WAVEFORM FOR CARRIER AND REFERENCE SIGNAL: TRANISTOR PARAMETERS:- IS=6.734F BR=0.7371 TR=239.5N BF=416.4 CJC=3.638P TF=301.2P CJE=4.493P

+

4

Rin2Mohm

1

Co10pF

+

R1

1kohmR2

1kohm

RF

100KohmRo

75ohm

VgSVr

Vi-2*10^5Vi

+

5

-

SVc

3

-

2

0

6

26

DIODE PARAMETERS:- IS=2.2E-15 BV=1800V TT=0; SUBCIRCUIT .SUBCKT NAME INV NONINV CONTROL+VE CONTROL-VE ---------------- ----------------- .ENDS NAME SYNTAX FOR THYRISTORS:- XNAME REFNODE CARRNODE GATE+VE GATE-VE Subcircuit should be included in the main program before defining thyristor. .INC sub circuit name .cir

27

6. ROOT LOCUS, BODE PLOT AND NYQUIST PLOT . AIM : To plot root locus, bode plot and nyquist plot of the transfer functions. Transfer Function 1: G(s) = 1 --------- (s+2)2 Transfer Function 2: G(s ) = s+2 ------------ s2+3s+1 Transfer Function 3: G(s) = 0.5s2+1.5s+1 ------------------- 10s2-9s-1 Transfer Function 4: G(s) = 1 -------------------- s4+5s3 +8s2+6s Transfer Function 5: G(s) = 0.164(s+0.2) (s+0.32) -------------------------------- s2(s+0.25) (s-0.008)

28

7. TRANSFER FUNCTION ANALYSIS OF A GIVEN SYSTEM.U SING MATLAB(SIMULINK )

AIM : Using Simulink obtain the response of given 3rd order system 2d3y + 4d2y + 8dy + 10y = 10u (t). dt3 dt2 dt

STEPS:- 1. CHOOSE STATE VARIABLES 2. EXPRESS IN STATE SPACE FORM 3. CONSTRUCT SIMULINK BLOCK DIAGRAM USING STSTE SPACE EQUATIONS 4. FIND THE STEP RESPONSE

29

8.POWER FLOW ANALYSIS USING GAUSS-SIEDEL METHOD

AIM: - USING GAUSS SIEDEL METHOD DETERMINE A)THE PHASOR VALUE OF VOLTAGES ATLOAD BUSES 2&3 B)FIND THE SLACK BUS REAL &REACTIVE POWERS,CURRENTS. C)THE LINE FLOWS &LINE LOSSES.

DEVELOP A PROGRAM FOR GAUSS-SEIDEL METHOD IN MATLAB. BASE MVA=100 V1=1.05∟00

0.02+j0.04

0.01+j0.03 0.0125+j0.025

256.6MW

110.2Mvar

138.6MW 45.2Mvar

1 2

3

Gen

1 2

3

30

9. PARAMETRIC ANALYSIS .

AIM:

The RLC circuit is supplied from a Step input voltage. Use PSPICE to calculate and plot capacitor voltage Vc from 0-400µs with a time increment of 1µs for R1=1Ω, 2Ω, 8Ω.

CIRCUIT DIAGRAM:-

STEP INPUT VOLTAGE: __ _ | | | | | |

L1

50UH

R1

1ohm,2ohm,8ohm

V4

C1

10UF

1ns 1ms

1v

V

t

31

.PARAM (PARAMETER ) Pspice allows on to use a parameter instead of a numerical value. This parameter can change into an arithmetic expression. The parameter definition is in one of the following forms; .PARAM PNAME=VALUE OR EXPRESSION The keyword PARAM is followed by a list of names with values or expressions. The value must be a constant and does not need to be enclosed in braces however the expression need braces , and must use only previous used parameters. PNAME is the parameter name EX:- Suppose in any circuit inductor value is changing 5MH,15MH,25MH.it can be defined as .PARAM LVAL=1MH L 3 4 LVAL .STEP (PARAMETRIC ANALYSIS) The STEP command can be used to evaluate the effects of parameter variations. It has one of the following general forms .STEP LIN SWNAME SSTART SEND SINC .STEP OCT SWNAME SSTART SEND NP .STEP DEC SWNAME SSTART SEND NP .STEP SWNAME LIST VALUES WHERE SWNAME is sweep name i.e variable name whose values are varying SSTART SEND SINC are start end and increment values of that variable NP-number of steps. EX:- STEP LIN VCE -5V 10V 5V STEP TEMPLIST 0 50 80 100 150 STEP PARAM FREQUENCY 8.5K 10.5K 50 Consider the above example L=5MH, 15MH&25MH Therefore that can be defined as .PARAM LVAL=1MH L 3 4 LVAL .STEP PARAM LVAL 5MH 25MH 10MH It means start value is 5MH; End value is 25MH with an increment of 10MH.

32

OP-AMP CIRCUIT MODEL

1. DC LINEAR MODEL 2. AC LINEARMODEL DCLINEAR MODEL :- An op-amp can be modeled as a voltage controlled voltage source. Input resistance is high, typically 2mega ohms and output resistance is very low (75 ohms).for an ideal op-amp the model is

THIS MODEL CAN BE FURTHER REDUCED TO ;( SINCER0<<<<<<RIN)

These models do not take into account the saturation effect & slew rate, which do exist in actual op-amps. Gain is also assumed to be independent of frequency but in practice gain falls with frequency. This model is suitable for dc or low frequency applications.

-

v1

1

4

-

+

RiAoV1

+ 3+

v1

2

5

-

Ro

-

v1

1

4

-

+

RiAoV1

++

v1

2

5

-

33

AC LINEAR MODEL :-HIGH FREQUENCY MODEL OF OP-AMP. Frequency response of an op-amp can be approximated by a single break frequency. If an op-amp has more than one break frequency. It can be represented by using as many capacitors as the number of breaks. FREQUENCY RESPONSE This model don’t take into account saturation effect and suitable only if op-amp operates with in the linear region

OUTPUT VOLTAGE ` VOUT=-A 0 V2

-A 0VIN VOUT = ---------------- 1+SR 1C1

WHERE S=j2пf -A 0VIN VOUT = ---------------- 1+ j2пf R 1C1

-

Ro

Vin

1

-

-4

7

-

+

+

RiV1/R1

+

C1R1

+

V2

+

2

3

-

VoutAoV2

A

f(HZ)

2*10^5

0 1M 10

34

-A 0 V IN VOUT = ---------------- 1+jf/fB WHERE fB = 1/ 2п R 1C1 A0-is large signal or dc gain of opamp Thus the open loop voltage gain is VOUT -A 0 A(f) = ----------- = ------------- VIN 1+jf/fB EX:-FOR741 OPAMP

Fb=10HZ , A0=2*105 , Ri=2M Ω , Ro=75Ω IF R1 IS 10 KΩ Then C1=1/(2п*10*10*103)=1.1562µF SYNTAX FOR OP-AMP XA NEGATIVENODE POSITIVENODE O/PNODE REFNODE OPAMPAC (INVERTING) (NONINVERTING) (SUB CIRCUIT NAME) Define ac linear model equivalent for opamp in sub circuit and name it as OPAMPAC.CIR To include that sub circuit in the main program .INC OPAMPAC.CIR before defining opamp syntax in main program HOW TO WRITE SUB CIRCUIT: .SUBCKT NAME NI+ NI- NO+ NO- --------------------------- --------------------------- .ENDS NAME In between .SUBCKT &.ENDS opamp ac linear circuit elements should be defined. NI+, NI- & NO+, NO- are input positive, negative nodes &output Positive, negative nodes of ac linear model of opamp.

35

10. INTEGRATOR USING OPAMP.

AIM :

For the given input voltage shown in figure plot the transient response of the output

voltage for duration of 0 to 4ms in steps of 50µs.

CIRCUIT DIAGRAM:-

INPUT WAVEFORM:

_ _ _ _ _ _ 1 2 3 4

R0

100kohm

U1A

LM324

1

3

2

411

OUT

+

-

V+

V-

C1

0.1UF

RF

1Mohm

R1

2.5Kohm

RX

2.5Kohm

v 2

v 1

15v

Vin

t (msec) 0

1v

-1v

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10. DIFFERENTIATOR USING OPAMP . AIM:

For the given input voltage shown in the figure plot the transient response of the output voltage for a duration of 0to 4ms in steps of 50µs CIRCUIT DIAGRAM:-

INPUT WAVEFORM: Vin

1v _ _ _ _ 0 1 2 3 4 t (msec)

RL

100kohm

U1A

LM324

1

3

2

411

OUT

+

-

V+

V-

r1

100ohm

RX

1k

v 2

rf

10kohm

v 1

15v

c1

0.4uf

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11.SINGLE PHASE CYCLOCONVERTER

AIM: To plot load voltage, load current and voltages across SCRs for a single phase mid point cycloconverter with R&L loads. CIRCUIT DIAGRAM:-

Vs2XT3

Va

0V

L

125mh

XT2

R

100ohm

+

-

-

XT1

1 A.C50Hz +

Vs1

o Vc

0v

XT4

Vb

0V

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12. CHARACTERISTICS OF JFETS

JFET can be used as a voltage controlled device and is used in power electronic applications. AIM: To plot the output characteristics if VDD is varied from 0 to 12V in steps of 0.2V &VGS is varied from 0 to -4Vin steps of 1V& to plot the transfer characteristics if VGS

is varied from 0 to -5V in steps of 0.1V & VDD=10V. MODEL PARAMETERS: IS=100E-14 RD=10 RS=10 BETA=1E-3 & VTO=-5

CIRCUIT DIAGRAM:-

A CIRCUIT WITH AN N-CHANNEL JFET.

The model statement of an n-channel JFET has the general form .MODEL JNAME NJF (P1=A1 P2=A2 ……………………………... PN=AN) EX: .MODEL SWITCH NJF (IS=100E-14 RD=10 RS=10 BETA=1E-3 VTO=-5)

Where JNAME is the model name: it can begin with any character and its word size is normally limited to eight characters. NJF is the type symbol of n-channel JFETS. P1, P2 ……………& A1, A2…………are the parameters and there values respectively. The symbol of JFET is J.The name of a JFET must start with J IT TAKES THE GENERAL FORM: J<NAME> ND NG NS JNAME EX: JQ 1 5 9 JMOD

J1

Vx

VDD

VGS