CD4046 SPICE model

.subckt CD4046 sigin phcmpii phcmpi phpls compin vcoin
+              r1 r2 ce1 ce2 vcoout demout inhibit zener vdd vss
+                   OPTIONAL: DPWR=$G_DPWR DGND=$G_DGND
+                   PARAMS: MNTYMXDLY=0 IO_LEVEL=0
+                   Rin=1Meg S1=1  S2=0.5 M1=0.5 M2=1.0 Vx=10
+                   Kb=1 Vfree=0.0 Kc=-0.1 Vt=1.2 Vxqr=10

* Rin  = VCO Input Resistace
* S1   = Voltage Limiter linear slope
* S2   = Voltage Limiter non-linear slope
* Vx   = Input threshold voltage (between S1 and S2)
* Kb   = Arbitrary constant to adjust the value of the conversion gain (transimpedance gain)
* Vfree= Frequency dependent constant in Emult
* Kc   = Negative inverse amplitude of the square wave
* Vt   = Trigger voltage of Schmitt trigger (not used)
* Vxqr = Amplitude of square wave (not used)
* M1   = Current mirror multiplier to adjust oscillator frequency
* M2   = Current mirror multiplier to adjust oscillator frequency

* Preliminary model still under development based on Natinal Semiconductor CD4046BM
* RAPerez 9/98

* Phase detector section

U1 INVA(4) DPWR DGND sigin compin isigin icompin
+                    isigin icompin clk1 clk2


U2 XOR DPWR DGND isigin icompin xorout

***tplhty=20n tphlty=20n

U3 NAND(2) DPWR DGND q1 q2 pclr

.MODEL NAND_TIMING UGATE (tplhty=1n tphlty=1n)

U4 DFF(1) DPWR DGND $D_HI clr clk1 $D_HI q1 qb1

.MODEL DFF1_TIMING UEFF tppcqlhty=4n tppcqhlty=4n tpclkqlhty=4n tpclkqhlty=4n

U5 DFF(1) DPWR DGND $D_HI clr clk2 $D_HI q2 qb2

.MODEL DFF2_TIMING UEFF tppcqlhty=5n tppcqhlty=5n tpclkqlhty=5n tpclkqhlty=5n

U7 BUFA(2) DPWR DGND fq1 fq2 s1 s2


ST2 vdd phcmpii s1 0 swt
SB2 phcmpii vss s2 0 swt

.model swt VSWITCH (ROFF=2G RON=10m VOFF=0.8 VON=3.0)

U6 AND(2) DPWR DGND pclr reset clr


Ureset STIM(1,1) DPWR DGND
+ reset
+   +0s 0
+   2ns 1
+   1s 1

U8 NOR(2) DPWR DGND fq1 fq2 norout


U9 ANDA(2,2) DPWR DGND q1 od1 q2 od2 fq1 fq2




U12 BUFA(3) DPWR DGND norout xorout vcosqr phpls phcmpi vcoout


* VCO Section

Rin vcoin vss {Rin}
Evlim vlim 0 value={if(v(vcoin,vss)<v(vdd,vss),
+                   S1*v(vcoin,vss),S2*(v(vcoin,vss)-v(vdd,vss))+v(vdd,vss))}
Rvlim vlim 0 1Meg
Emult mix 0 value={v(vlim)*Kb+Vfree}
*Hmult mix 0 poly(1) Vcm 1.44 0.586
Rmult mix 0 1

Edemout demout 0 table={ 200Meg*v(vcoin,demout)*v(off) } (-20,-20) (20,20)
Rdemout demout 0 1Meg
ER2 ir2 0 vdd ir2 200Meg
VR2 ir2 r2
ER1 ir1 0 mix ir1 200Meg
VR1 ir1 r1
Eosclg adj 0 table={abs((V(vdd)/I(VR2))/(V(mix)/I(VR1)))}
+ (0.5,1.43) (1,1.6) (10,1.04) (50,0.67) (100,0.84) (101,1)
+ (102,1) (1000,1)
Radj adj 0 1G
*GIM ce1 0 value={(M1*I(VR1)+M2*I(VR2))*Kc*V(sqrrc)}
GIM ce1 0 value={(M1*I(VR1)*V(adj)+M2*I(VR2))*Kc*V(sqrrc)}
*GIM ce1 0 value={(24*I(VR1)+3.067*I(VR2))}
Vcext ce2 0
Cstray ce1 ce2 6p
Rcext ce1 ce2 1T
Etrngl trngl 0 ce1 0 1
Rtrngl trngl 0 1Meg

Esqr sqr 0 value={-10Meg*V(trngl)+1.2Meg*V(sqrrc)}

Rsqr sqr sqrrc 0.1T
Csqr sqrrc 0 10f
Dsqr1 sqrrc 13 Diode
Vsqr1 13 0 {Vx}
Dsqr2 14 sqrrc Diode
.model Diode D (IS=10u N=0.1 CJO=80f RS=1m)
*.model Diode D (IS=10u N=0.001 CJO=80f)
Vsqr2 14 0 {-Vx}
Ipls 0 sqrrc pwl 0 0 10n 0 20n 0.01u 0.1u 0.01u 0.12u 0 1 0
Evcoout vcosqr 0 table={5.0*v(off)*(v(sqrrc)/Vx)} (0.1,0.1) (4.5,4.5)
*Rvcoout vcosqr vcosqr1 1

**Et 7 0 TABLE {-10k*V(trngl)+1.2k*V(sqrrc)} (-2,-10) (2,10)
*Ipls 0 sqrrc pwl 0 0 10n 0 20n 1u 0.1u 1u 0.12u 0 1 0
*Et 7 0 value={table({-10Meg*V(trngl)+1.2Meg*V(sqrrc)},-10,{-Vx},10,{Vx})}
*Ro 7 sqrrc 100
*Co sqrrc 0 100p

*Est sqrrc o VALUE={table({2000k*(V(st)-V(trngl))},-2,{-Vx},2,{Vx})}
*Rst1 sqrrc st 8.8k
*Rst2 st 0 1.2k
*Cst st 0 200p ic=-10

Rinhbt inhibit 0 1Meg
Eoff off 0 value={if(v(inhibit)<0.9,1.0,0.0)}
Roff off 0 1Meg

Dzener vss zener znr
Rzener vss zener 1G
.model znr D(Is=1.004f Rs=.5875 Ikf=0 N=1 Xti=3 Eg=1.11 Cjo=160p M=.5484
+  Vj=.75 Fc=.5 Isr=1.8n Nr=2 Bv=5.2 Ibv=27.721m Nbv=1.1779
+  Ibvl=1.1646m Nbvl=21.894 Tbv1=176.47u)


    Arduino Simulation Projects using Arduino Simulation Library Models.

    We have already seen in the article “ARDUINO Simulation PCB and 3D Models Libraries for Proteus”,  how to add the ARDUINO simulation, footprints and 3D models libraries to Proteus. Now we are going to see how is simple to use this components models for simulating ARDUINO projects. We can download for example the controlling LED project implemented with a microcontroler:


    Simple project implemented with a microcontroller model

    Fig. 1 Simple project implemented with a microcontroller model

    We can replace the microcontroller, capacitors and crystal oscillator with the ARDUINO UNO simulation model:

    The same project above implemented with ARDUINO UNO simulation model

    Fig. 2 The same project above implemented with ARDUINO UNO simulation model

    Let ‘s note that the PB5 output has a different numeration in the two models, but the .hex file should work for both, and also for the project implemented with ARDUINO Pro Mini model.

    Click the right mouse button, over the model, and choose “Edit Properties”:

    Edit Properties

    Fig. 3 Edit Properties

    Load the hex file of the blink project in the “Program File” edit field:

    Load the Hex file

    Fig. 4 Load the Hex file

    finally, let ‘s run the simulation:

    Run th simulation

    Fig. 5 Run th simulation

    Regarding the PCB assignment, let ‘s note that the only component that hasn ‘t an assigned footprint is the animated red LED:

    Fig. 2 PCB package not specified for the LED component

    Fig. 6 PCB package not specified for the LED component

    We have to assign one to it: select the component, right mouse button, and let ‘s choose “Make Device”:

    Make Device window

    Fig. 7 Make Device window

    Click onNext, and the “Add/Edit”:

    Click on "Add/Edit" button

    Fig. 8 Click on “Add/Edit” button

    It ‘s shown the “Package Device” window:

    Package Device window

    Fig. 9 Package Device window

    Click on “Add” button and type the keyword “led” on the “Pick Packages” window, and select LED PACKAGE

    Type "led" on Pick Packages window

    Fig. 10 Type “led” on Pick Packages window

    Double click over the first line, under the letter “A”

    Double click

    Fig. 11 Double click

    and click on the anode pin of the PCB:

    Click on Anode pin

    Fig. 12 Click on Anode pin

    Same procedure for the other pin:

    Click on Cathode pin

    Fig. 13 Click on Cathode pin

    Now, let ‘s click on the “Assign Packages” button,

    Packagings window shows the PCB assigned

    Fig. 14 Packagings window shows the PCB assigned

    Next button, select PACKAGE from the Component Properties and Definitions options:

    Select PACKAGE

    Fig. 15 Select PACKAGE

    Leave blank the Datasheet Filename edit field:

    Fig. 16 leave blank the datasheet field

    Choose USERDVC library, for example:

    choose USERDVC library

    Fig. 17 choose USERDVC library

    Confirm the update request in the next message box

    Fig. 18 Update message box

    ARDUINO Simulation PCB and 3D Models Libraries for Proteus.

    Arduino is an hardware/software open-source microcontroller board. It has been widely accepted in the hobbistic, educational and professional communities due to its versatility, ease of use and programming. This tutorial explains step by step how to simulate, visualize the layouts and 3D models of ARDUINO UNO, ARDUINO MEGA, and ARDUINO Pro mini boards in Proteus.

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    SPICE simulation with Proteus of a Coils Tester.

    Ing. Cristoforo Baldoni

    This article deals with the Proteus simulation (version 7 and higher) of a low cost and very useful coils tester, easy to build by yourself. It ‘s the In-circuit LOPT (Line OutPut Transformer) Tester by Bob Parker that allows to evaluate the smooth functioning of a coil by turning on a number of different colored LEDs. It doesn ‘t measure the inductance value of a coil, but rather the ratio of its resistive part and the inductive part. This tester is very useful in finding coils with shorted turns, and wound components like yoke windings and SMPS transformers. Low loss components, will turn on four or more LEDs, while components with short circuits will turn on few or no LEDs. We ‘ll se how to implement and simulate with Proteus the circuit which consists of three sections: the low frequency pulse generator, the ring amplitude comparator and the LED bargraph display. We ‘ll se how to model a coil and try different values for the inductive and resistive component to validate the simulation. The Proteus simulation files of the device are available for download after accessing this article.


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    Circuit-Breaker Model for Over-Current Protection Simulation of DC Distribution Systems.



    Abstract: This article describes an electrical model of a thermalmagnetic circuit-breaker that can accurately simulate characteristic behaviour over a wide range of overcurrents, including operation in the magnetic region. The model has been validated against measured waveforms from both a high-current DC test facility and a distributed power system rack. The circuit-breaker model can be coupled with other distribution component models to simulate the protection performance in telecommunications DC distribution systems.



    The design and analysis of over-current protection for telecommunication DC power systems can be greatly assisted by the use of a computer-aided simulation tool. However, a simulation is only as accurate as the component models and element values used to represent the real world. This article reports on the development of a circuit-breaker model that can accurately represent circuit-breaker behaviour over a wide range of overcurrents.

    The performance of protection, distribution and storage devices significantly affects both the reliability and safety of the DC power system. Voltage excursions caused by an over-current instance can cause electronic equipment to malfunction due to over-voltage, and disrupt service due to under-voltage. Poor discrimination between protection devices can cause upstream device operation, resulting in major interruption to service. The rapid advancement of both computing power and analogue circuit simulation programs derived from SPICE software provides a relatively user-friendly environment for over-current protection design and analysis. This is advantageous as telecommunications power distribution systems are often large and complex, and developing an equivalent circuit model for a power system is not a trivial task.

    The circuit-breaker model described in this article implements the enhanced modelling functions available with PSpice’s Analog Behavioural Modelling to include circuit-breaker current, time and arcing dependent characteristics. This model complements and extends previously published modelling work [1-2] by Telstra Research Laboratories on other power system components.


    2.Circuit-Breaker Characteristic Operation

    A typical thermal-magnetic circuit-breaker operates (trips) in two distinct modes; the thermal mode occurs for device currents from 1 up to about 10-15 times the rated setting current, and the magnetic mode occurs for all current levels above the thermal operating region. Characteristic current-time curves for the device operating in the thermal region can be approximated by an equation where i n t equals a constant, whereas in the magnetic region the operating time (typically <20ms) is not well defined in device data curves and specifications, as test circuits are based on rectified AC power sources which have typical rise times exceeding a few milliseconds.

    The circuit-breaker model presented in this paper has been developed for a 125A moulded device (10kA fault rating), which is commonly used to protect individual battery strings within Telstra’s distributed power supplies.

    For device operation in the thermal region, the characteristic i n t form of the current-time curve can be obtained from the device specification curve as shown in Figure 1. A value of n = 3.5 gives an adequate fit over the range of currents within the thermal operating region.

    Fig.1 125A circuit-breaker current-time operating boundary curves (courtesy of GEC ALSTHOM AUSTRALIA).

    Fig.1 125A circuit-breaker current-time operating
    boundary curves (courtesy of GEC ALSTHOM



    For device operation in the magnetic region, characteristic current-arc voltage-time behaviour has been observed for the circuit-breakers operating in a high-current DC test facility over a range of current levels and circuit time constants. At the start of such a fault instance, the current passing through the closed circuit-breaker contacts increases to a level where magnetic activation forces the contacts to open. As the contacts start to open an arc is developed which is inherently unstable and a complex voltage-current characteristic occurs as the arc progresses through to extinction.
    For the 125A circuit-breaker operating in the magnetic region, the contacts are forced open when the current level typically rises above 2-4kA. Circuit-breaker operation was measured over a range of circuit conditions, such as:

    · fast rates of current rise exceeding 10kA/ms, which resulted in short pre-arcing times of about 0.15- 0.2ms (eg. results from a test circuit with 5.4kA prospective current and 0.26ms time constant are shown in Figure 2).

    · high prospective current levels exceeding 10kA, which result in pre-arcing times around 0.9ms for circuit time constants of about 1.2ms, as shown in Figure 3. It should be noted that special oscilloscope probing and current shunt techniques are required to record clean waveforms in the high transient noise environment that occurs in a high current test facility.

    Fig.2 Measured current and voltage waveforms for a 125A circuit-breaker operating in 54VDC test circuit with 5.2kA prospective current and 0.25ms prospective time constant; 1kA/div current, 20V/div voltage and 0.5ms/div.

    Fig.2 Measured current and voltage waveforms for
    a 125A circuit-breaker operating in 54VDC test circuit
    with 5.2kA prospective current and 0.25ms prospective
    time constant; 1kA/div current, 20V/div voltage and

    Fig. 3 Measured current and voltage waveforms for a 125A circuit-breaker operating in 54VDC test circuit with about 12kA prospective current and about 1ms prospective time constant; 1kA/div current, 50V/div voltage and 0.5ms/div.

    Fig. 3 Measured current and voltage waveforms for
    a 125A circuit-breaker operating in 54VDC test circuit
    with about 12kA prospective current and about 1ms
    prospective time constant; 1kA/div current, 50V/div
    voltage and 0.5ms/div.

    Fuse Model For Over-Current Protection Simulation of DC Distribution Systems.

    T. Robbins
    Telecom Australia Research Laboratories
    770 Blackburn Road, Clayton, 3168


    Abstract: The design and analysis of over-current protection for telecommunication DC power systems can be greatly assisted by the use of a computer-aided simulation tool. This article reports on the development of a fuse model for SPICE derived software that can accurately represent characteristic fuse parameters. The fuse model can also be adapted to represent the operation of circuit breakers.



    The design and analysis of over-current protection for telecommunication DC power systems can be greatly assisted by the use of a computer-aided simulation tool. However, a simulation is only as accurate as the component models and element values used to represent the real world. This article reports on the development of a fuse model that can accurately represent fuse characteristics. The fuse model can also be adapted to represent the operation of circuit breakers.
    The performance of over-current protection devices significantly affects both the reliability and safety of the DC power system. Voltage excursions resulting from the operation of a fuse during a short circuit can cause electronic equipment malfunction due to over-voltage, and disrupt service due to under-voltage. Poor discrimination between protection devices can cause upstream device operation, resulting in major interruption to service.

    The rapid advancement of both computing power and analogue circuit simulation programs derived from SPICE software provide a user-friendly environment for over-current protection design and analysis. This environment is advantageous as telecommunications power distribution systems are often large and complex, and developing an equivalent circuit model for apower system is not a trivial task.

    The analysis of DC distribution systems using computer simulation has been shown to provide fair agreement between simulated and experimental results [1,2,3]. However, the fuse models developed have not been able to accurately represent fuse characteristics. Typical parameters for a fuse operating in a circuit with a given time constant and prospective current are rated current ir, peak current ip, pre-arcing time tp, arcing time ta, total operating time tt= tp + ta, pre-arcing i²t (i²t)p, arcing i²t (i²t)a and total operating i²t (i²t)t= (i²t)p + (i²t)a. Figure 1 illustrates some of these parameters. The prospective current for a circuit is the maximum current that would be reached if the fuse did not operate.

    The i²t or current-squared time rating is a commonly used fuse characteristic when operating current levels are much higher that the rated fuse current ir. The circuit time constant defines the ratio L/R, where L and R are the effective circuit inductance and resistance components in series with the fuse and energy source.



    Typycal fuse parameters

    Fig 1. Typycal fuse parameters

    A fuse model is developed in Section 2 and model validation is undertaken in Section 3. Section 4 discusses the development of other DC power system component models for application to the analysis of over-current protection, and the paper is summarised in Section 5.

    Straightforward Method to Design and Simulate with SPICE the Loop Compensation Controller for All Switching Power Supplies.

    Ing. Cristoforo Baldoni

    In this article we ‘ll see how to find the output power stage transfer function H(s), called the Control-to-Output function,  of the most switching power supplies: BUCK, BOOST, BUCK-BOOST, HALF-BRIDGE, FULL BRIDGE, both in voltage mode control and current mode control. In spite of the complexity of the different types of power supplies that use one or more output feedback, the output power transfer function H(s), can be reduced to a few schematic categories of general validity. We’ ll see when it’s the case to consider the effects of the RHPZ, the Right Half Plane Zero, and what it means in practical terms.
    Once the components for the specific power supply have been sized, we can estimate with good approximation the transfer function which describes mathematically the output power stage. As seen in the article about the determination of POLES and ZEROS by inspection,  we ‘ll identify immediately the POLES and ZEROS which characterize the different switching categories.
    We ‘ll draw the Bode plots of these functions with PSpice, and, according to their characteristics, we ‘ll choose the most suitable compensator G(s), implementing the compensation network with the operational amplifiers embedded in the microcontrollers. The SPICE simulation of the open loop transfer function G(s)*H(s), will allows us to evaluate the results for the system stability. Finally, we ‘ll apply this method in two real switching power supply: a low power flyback converter and an off-line, half-bridge switching.
    This method allows us to speed up the design of the compensator G(s) in the prototyping phase before the physical measurement with the instrumentation.

    It’s strongly recommended the reading of these articles:

    Accessing this article you can download the following SPICE simulation files about switching power supply compensation design:

    -Forward function example

    -Flyback function example

    -Flyback function example with a Right Half Plane ZERO

    -Origin POLE compensator

    -Origin POLE Transfer function implementation

    -Forward function compensated example

    -One ZERO two POLES compensator

    -One ZERO two POLES Transfer Function Implementation

    -Flyback with RHPZ compensated

    -Three POLES two ZEROS compensator

    -Three POLES two ZEROS Transfer Function

    -Transfer function of a real Flyback converter

    -Compensator for the flyback converter

    -Overall compensated  transfer function of the flyback converter

    -Transfer function of a real Forward converter

    -Compensator for the Forward converter

    -Transfer function of compensator for the Forward converter

    -Overall compensated  transfer function of the Forward converter

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    SPICE simulation of a Combo Wave Generator.

    Thanks for this article to ssleandro


    In this article we ‘ll se how to implement a template for a Combination Wave Generator that can be a Surge Generator, a Line Impedance Stabilization Networks (LISN), motor control, ripple current, etc. This model can be very useful for hardware engineers which can utilize it in their projects to speed up project development. The platform used for the simulation is PSpice but
    it can easily replicated in other SPICE simulation software.


    The simplified model of the GPM consists of an High-Voltage source U, a charging resistor Rc, an energy storage capacitor Cc. This part of circuit is connected by a switch to 2 Pulse duration shaping resistors Rs, an impedance matching resistor Rm and a Rise time shaping indutor Lr, as in the picture below





    typical values of this components are:  Cc=7.76μF,  Rs1=14.8 Ohm,  Rm=1.05 Ohm,  Lr=9.74μH,  Rs2=23.3 Ohm. The peak voltage on Rs2 can be 1KV, 2KV,..6KV.


    In the following schematic we set the high voltage with the initial condition of the CapacitorCc, for example for 6KV, we set 6300 in the PSpice IC field of the Cc component. We can adjust the time in U1 to make surge hit at 90/270 degree or whatever phase we want.







    Calibration of Surge Generator.

    The IEC/EN 61000-4-5 standars requires the following waveform of open-circuit voltage with no Coupling/Decoupling network (CDN) connected




    This is the result of the simulation that shows a voltage waveform that fullfills requirementof IEC/EN 61000-4-5





    Below the image of the waveform of short-circuit current with no CDN connected




    and here again the simulated results:




    Ipeak is about 1.5KA, T1 is 8uS and T2 is 20uS. The effective coupling impedance is 2Ohm. The simulated current waveform fulfills requirement of IEC/EN 61000-4-5 standards.

    Designing and Simulation of Industrial PID Controllers using Microcontrollers

    Ing. Cristoforo Baldoni

    In this article we’ll see how to pass from the design of analog PID controllers for continuous-time systems to digital controllers, replacing operational amplifiers, resistors and capacitors with microcontrollers. Digital controllers are very compact, all the controller fits on a chip, including the A/D and the D/A converters, moreover, digital controllers are not affected by the aging of the components and don’t change their values with the temperature as analog components do. We’ll see how to apply the Z-transform, the equivalent of the Laplace transform, but for discrete-time systems, we’ll see how to identify the transfer function of a process and we’ll explain, with a step by step procedure, how to apply the theoretical knowledge learnt by examining an Proteus microcontroller based project, that uses its PWM output to control an oven ‘s temperature. The microcontroller has a 10 bit A/D converter. This procedure can be easily adapted with minimal adjustments to other processes to control.



    1. Digital Control-System Block Diagrams


    2. Linear difference equations, Z-Transform, Inverse Z-Transform and Discrete Transfer Function.


    3. Sampling and A/D Analogic to Digital Converter


    4. D/A Digital to Analogic Converter and ZERO ORDER HOLD  (ZOH) : Relationship between the Continuous Transfer Function and Discrete Transfer Function of a sampled Process.


    5.  Block Diagram Manipulation of Sampled Data Systems


    6. Methods for designing Digital Controllers, Stability.


    7. Designing  PID controllers by microcontrollers


    8. Transfer Function Identification and PID Tuning using the Ziegler–Nichols Method.


    9. Practical case of a temperature control system implemented with a microcontroller PIC and simulated with ISIS Proteus: Step by step explanation of how to apply the theoretical knowledge for implementing and simulating a PID controller.

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    Designing Industrial PID Controllers using SPICE

    1. Design of PID regulators , design and test with SPICE simulation



    2. Easy way to implement compensators with operational amplifiers






    1. Design of PID regulators , design and test with SPICE simulation

    Graphical method

    Let’s examine now a graphical method for designing P.I.D. controllers. P.I.D. are Proportional-Integral-Derivative controllers and represent one of the techniques widely used to implement industrial control systems. Below the diagram block of a typical feedback system

    Figure 1 – Generic feedback system

    There are several types of compensators, in series, in feedback and combinations of both. The compensator in series is the most used. A compensation system is required when the closed loop system is unstable, when the system is stable but the steady state error or the dynamic behavior doesn’t meet the required specifications, or both. To compensate the system we put before the process (in series) a controller whose transfer function is R(s), as you can see in the figure below

     Figure 2 – Compensated feedback system

    The generic transfer function introduced by the P.I.D. controller can be expressed as:


    P.I.D. controllers can exist also as a simple P controller (KD = KI =0), as a P.D. controller (KI = 0), or as a P.I. controller (KD =0). The proportional contribute of a P controller can improve the specification about the steady state error, the derivative contribute increases the damping of the closed loop system and the integrative contribute increases the type of the system, and then can eliminate or improve the steady state error.


    The simplest version is the proportional controller P. Its transfer function is:


    This type of controller can improve the specification on the steady state error, but at the same time increases the bandwidth of the feedback system which means a faster response of the system to follow the reference but a decrease of the stability margins.  For a system with unitary feedback and open loop transfer function equal to F(s) the steady state error is:


    multiplying by the gain Kp the new error will be


     let’s see a practical example, the open loop transfer function of a unitary feedback system is


    Figure 3 – Implementation of open loop function with Laplace PART in PSpice

    The bode plot of the transfer function is:


    Figure 4 – Bode plot of gain and phase

    The specification on the system requires, for example, a steady state error equal to 3% and a phase margin PM of 50 degrees.It’s:


    we have to impose



    we get KP= 388.

    Plotting the compensated function we get


    Figure 5 – Bode plot of function compensated with proportional controller

    The phase corresponding to the crossing frequency is about -156 degrees

    Figure 6 – Phase at crossing frequency

    the specific on the phase margin can’t be satisfied with only the proportional compensation.