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Introduction to Spice

1. SPICE input file Title This must be the first line Description of the circuit s function Circuit Elements three kinds Sources Passive Circuit Elements Active Circuit Elements Model Statements Analysis Requested Output form Requested END Before saving the file make sure to press return once and only once after you type this statement The denotes a comment description or statement added by the writer of the spice code Any designated line with at the beginning will be skipped by the complier and will not have an effect on the actual code Any descriptions or comments can be omitted and the program will execute the exactly the same way Any comments descriptions or statements are for nothing more than the convenience of the reader The Circuit Elements category describes all the physical components that are contained in the circuit schematic Analysis Requested and Output form Requested are tools that are implemented in order to view a desired response from the circuit The end statement tells the compiler that the input file is finished Don t worry too much about capitalizing letters SPICE is case insensitive Circuit Elements Statements Each element is described to spice in the input file by an element statement These statements contain the element name the nodes where the element is located and the physical characteristics of the element The first letter in the element
2. The pulse spends 5 seconds at 5V and has a total period of 10 seconds EXP Generic Vname n n EXP v v2 tdl taul td2 tau2 Example V11 11 0 EXPC 2 lu 5u 3u Lu VI is the starting voltage V2 is the maximum voltage tdl is the time in seconds to wait at the starting voltage before changing to the maximum voltage taul is the time constant for the change from the starting voltage to the maximum voltage td2 is the time in seconds to wait from time t 0 before changing back to the starting voltage tau2 is the time constant for the change back to the starting voltage The example details an exponential voltage named 11 It is connected to nodes 11 and 0 It starts at 1 volt and waits lus before it starts to rise to 2V with a time constant of 5u At 3us it stops rising and starts to fall back to 1V with a time constant of 1u PWL Generic Vname n n PWL tl vl t2 v2 tn vn Example V100 25 10 PWL O 0 3e 3 5V 6e 3 5V 10e 3 3V To use a piecewise linear source state a voltage and the corresponding time you wish the source to reach that value In the example above at time 0 the source will have a value of OV The source will then perform a linear increase for the next 3ms till it reaches 5V The next point given has the same voltage value so the source will have the value of 5V for the next 3ms The source will then follow a linear degradation till it reaches 3V four milliseconds later Graphs of the time varyin
3. needs to be valid is your email After you complete the form an email will be sent to you with a link to download the software 4 Click on the link in the email and download and install the OrCAD Demo Software OrCAD 16 5 Demo Software Capture and PSpice only 5 You are now ready to run PSPICE A D lite NOTE If you use a MAC computer you can try running LTspice IV or PSPICE A D lite using WINE You will have to do your own research to figure this out The LTspice manual talks about this procedure To simulate a circuit With SPICE you will need to first create a netlist A netlist is a text file that describes the circuit and analysis desired You then simulate the netlist and after simulation you are able to view the results from the analysis requested For LT spice 1 Go to File gt Open 2 On the bottom of the pop up where it says Files of type change this to Netlists cir net sp 3 Type in the desired file name ending with cir 4 When LTspice asks you if you want to create a new file click yes For Pspice 1 Go to File gt NewText File NOTE When saving a file in PSPICE save it as filename cir In order to simulate the PSPICE file you must first close the file and then reopen it Now you have a blank netlist file for you to write your netlist to be simulated Note that every spice netlist starts with the name of the file and ends with the end statement Netlist This is a model of a typical
4. statement identifies what type of element the statement is for The next two two terminal device three three terminal device four four terminal device etc characters of the statement are for the node numbers that the terminals are connected to The last part of the statement contains the physical model of the element If certain device physical characteristics are left blank then Spice has a set of default values that it will automatically use Even though SPICE has some default values for a limited number of device characteristics some parameters cannot be left blank Table 1 1 contains a list of some basic elements and the letter that is used to identify them Table 1 1 Device Letter abbreviations First Letter Capacitor Voltage controlled voltage source VCVS Current controlled current source CCCS Voltage controlled current source VCCS Independent current source Resistor Independent voltage source Current controlled voltage source VECS i sf O Q These elements fall into three different categories Signal Sources Passive Elements and Active Elements Voltage source Current source co it fit Vname Figure 1 1 Independent Sources Independent Sources Three independent sources can be used in SPICE simulations A DC source a frequency sweeping AC source and time varying signals all can be modeled with standard SPICE signal sources Each source can either supply current or voltage Different typ
5. Jonathan Roderick Onder Oz Tyler Rather EDITED BY Aaron Curry Experiment 1 Introduction to SPICE Introduction This experiment is designed to familiarize the student with SPICE SPICE simulations will be needed for prelabs and projects contained in this lab manual Spice is an acronym for Simulation Program with Integrated Circuit Emphasis SPICE is a computer aided design CAD tool that should be used to support design and should never be used in place of traditional design methods Design by SPICE is a trap that many circuit designers fall into and it causes a designer to lose the insight that makes one truly successful There are many different variations of SPICE that are produced by a few companies Two of such versions are LTSPICE provided for free by Linear Technology and PSPICE provided for free by Cadence In the past EE348 has taught students how to run HSPICE via the linux servers provided on campus However the graphical user interface GUI that the linux server has is much worse than that of freely distributed software Therefore this Lab shows how to use LTSPICE and PSPICE For the most part SPICE code is universally accepted by SPICE engines However there are some differences in available commands and syntax from version to version Therefore if any problems are encountered by the version of SPICE you are using you need to look at the reference manual to make sure you are using it properly Links to the SPICE manuals fo
6. _probe can be used with PSPICE no command is needed for LTSPICE and the built in wave viewers can be used After you have entered all the elements analysis and output request you must end the input file with an END statement Make sure to press return after you have typed your END statement Not doing this sometimes hang ups SPICE Graphical Interface Plots In order for LTSPICE to plot a desired trace first simulate your circuit by going to Simulation gt Run or by clicking the run button ki After the simulation is done the waveform viewer will automatically open In order to add a trace go to Plot Settings gt Add Trace A window that looks similar to the following will come up Only list traces matching Available data Z Asterisks match colons Cancel V 2 I Fi1 frequency Expression s to add 4 AutoR ange Figure 1 9 Window that appears in LTSPICE when adding traces From this window you can add traces by selecting them and clicking OR In PSPICE if you have the PROBE command entered the waveform viewer will automatically open after the simulation is done First simulate your circuit by going to Simulation gt Run or by clicking on the run button We Then you can add traces by going to Trace gt Add Trace A window that looks similar to the following will come up Add Traces M M L Simulation Output Variables Functions or Macros Analog Operat
7. ce and bulk are connected to nodes 15 O ground O ground respectively SPICE sources the Model called typical for its physical characteristics The new addition of L and W describe the physical dimensions of the device L stands for the length of the channel while W stands for the width The type of MOSFET is identified in the model statement In this example the MOSFET is a NMOS but replacing the NMOS part in the statement with PMOS will change the type of MOSFET from NMOS to PMOS A table of other typical MOSFET characteristics and their default values are listed in table 1 7 Fieve 20 lambda amma Command Statements Once you have entered all the element statements in the input file you have to enter the command statements These command statements tell SPICE exactly how you want to simulate the circuit and present the data As opposed to element statements all command statements begin with a period Analysis type Once the element statements are complete the analysis that is to be done needs to be specified to SPICE This is done with an analysis request statement When creating an input file you must decide from the start what type of analysis you want to perform As listed in table 1 2 some independent sources only work with certain types of analysis There are four basic types of analysis to choose from DC operating point DC sweep AC frequency response and transient response An example of each a
8. characters are also valid in SPICE to all the nodes in your circuit when writing an element statement You may number or name them anyway you wish with the exception of ground Spice interprets node zero as the ground The type of signal is identified after the node numbers An example of each will be demonstrated DC Generic statement Vname n n DC value Example V1 10DC 10V This is a DC voltage source with a value of 10V named 1 and its connected with its positive terminal at node 1 and its negative terminal at node 0 ground The name is arbitrary you can call it anything you want AC Generic statement Vname n n AC mag phase Example Vnew 50 AC 5V 2 This statement describes a frequency swept AC source called new that is connected to nodes 5 and 0 has a magnitude mag of 5V and contains phase shift of 2 degrees The phase can be left blank and SPICE will assume a zero degree phase shift SIN Generic statement Vname n n SIN Vo Va freq td theta phi ncycles LTSPICE only Example Vinput 2 1 SIN OV 5V 10e3 5e 3 0 0 0 Vo is the initial voltage Va is the voltage amplitude freq is the frequency in Hz td is the time delay in seconds theta is the damping factor This is used to apply an exponential decay to the sinusoid theta is the decay constant in 1 seconds phi is the phase advance in degrees Set this to 90 if you need a cosine wave form ncycles is the number of cycles of the p
9. d for homework 1 problem 5 3 The circuit in figure 1 13 is the problem 05 a Given Rs 50 ohms R2 800 ohms R1 80 ohms RI 50 ohms Ro 20 ohms Ao 20 Simulate figurel 13 c to show what Vo Vs is b Given Rs 50 ohms R2 800 ohms R1 80 ohms RI 50 ohms Ro 2 ohms Ao 2000 Simulate figure1 13 c to show what Vo Vs is c Please explain in a sentence or two what caused the difference in between part a and b General Report Format Guidelines 1 Introduction Explain what the lab is about Describe the circuits being built in terms of structure and purpose Also talk about what is being investigated 2 Procedure Step by step talk about what was done and show diagrams of the circuits 3 Data Present all data taken during the lab It should be organized and easy to read 4 Discussion Discuss the results you obtained What significance is there in the results How do they help your investigation Explain the meaning the numbers alone aren t good enough 5 Questions Answer all the questions in the lab 6 Conclusion Wrap up the report by giving some comments on the lab Do the results clearly agree with what the lab was trying to teach Did you have any problems Suggestions
10. el Statement section Model normal NPN Is 3e 14 Bf 150 Vaf 30V The example statement describes a BJT with its collector connected at node 3 base connected at node 14 and emitter connected at node 5 It references the model statement called normal for all the physical characteristics normal indicates to Spice that the BJT called 1 is an NPN transistor and gives some associated characteristics The Model statement is easily modified to change the transistor to a PNP type Simply replace the NPN with PNP in the statement Table 1 6 give some basic characteristics variables for a typical BJT and the default values associated with each Forward Early MOSFET Figure 1 8 Schematic symbol of MOSFETS gt is the Gate terminal D is the Drain terminal S is the Source terminal B is the Bulk terminal The element statement structure for the MOSFET is basically the same as the BJT but with one more terminal An example is given and explained below Generic under device section Mname DGS B Model_name L value W value under Model Statement section Model model_name NMOS certain parameter 1l value certain parameter 2 value etc Example under device section M55 3 15 0 0 typical L lu W 20u under Model Statement section Model typical NMOS kp 10u Vto 1 5 lambda 0 The MOSFET described by the example is called 55 Its drain is connected to node 3 while the gate sour
11. es of sources are used for different types of analysis Table 1 2 lists the different element statements for independent sources and the analysis type that is typically used with each Table 1 2 Suuwece elect slalermneuls Type of Signal Type of analvsis Element statement All types Vname nt n DC value DC Current Iname n n DC value AC Voltage Frequency sweep Vname n n AC mag pha AC Current Frequency sweep name nt n AC mag phase SIN wave Voltage Vname nt n SIN Fo Fa freg ta damping SIN wave Current Transient Iname n n SIN Fo Fa freg ta damping Pulse wave Voltage Vname nt n PULSE F Fz ta tr t PW T Pulse wave Current Iname n n PULSE F Vo ta t tp PW T Piecewise linear Voltage Transient Vname nt n PWL f v7 t2 v2 f Vn Piecewise linear Current Transient Iname n n PWL vi fo V2 ty Vrs Each element statement has an array of characters that represent different characteristics of the source The characters are separated by a space so that the compiler knows that the user is done describing one aspect and starting another In the element statements the first letter depicts if the source delivers voltage or current with a V or I respectively The first letter is followed by the name of that source Each source has to have a different name and they can be up to seven characters long Next the n and n denote the node number of the positive and negative terminal respectively You will assign numbers alphabetic
12. espect to Vin The first example finds the transfer function from the node called out to Vin The second example finds the transfer function from the differential voltage from nodes 2 to to Vin The third example finds the transfer function from the current in the resistor called out to Vin NOTE in PSPICE when the output variable is a current it is restricted to be the current through a voltage source Output requested With PSPICE you can request the data collected to be in the form of data points or as a plot This is done with a PRINT or PLOT statement The type of print or plot statement depends on what type of analysis you requested Table 1 8 lists these statements Table 1 4 Output data type requests Output requested Analwsis Spice Command Print data points i po TRAN UO el Plot data points PLOT DC output Pp oT TRAN You will be able to view the data collected in the output file that is created once you simulate the input file through PSPICE The output gives information on what you are measuring you can measure voltage voltage difference or current through any element and the node number where you want to observe the activity of the circuit You many request data from multiple outputs just separate the output requests with a space LTSPICE does not create an output file If you want to view the operating point again it can be found in filename op raw Table 1 9 lists different out
13. ex conjugate of x For adding expressions of traces in PSPICE all the available functions are listed on the right hand side of the add trace window Simply click on the trace on the left then click on the expression you want to be performed on the trace on the right Example of an input file Example input file x Vs2 0 SIN OV 1V 10k R1 2 1 10k D1 1 0 diode x MODEL diode D Is 2E 13 N 1 1 OP TRAN 0lm Im PLOT TRAN V 1 END Note SPICE is case insensitive A Schematic of the example input file Figure 1 11 Schematic of example input file The netlist and plots of nodes 1 and 2 as seen in LTSPICE fe 47 Uspice IV Example input file s 2 e File Edit View Simulate Tools Window Help A ed BASS l 5S FY Example input file sp Example input file sp w Example input file sp o E amp Example input file Us 2 6 SIN OU 1U 16k R1 2 1 16k D1 1 6 diode MODEL diode D Is 2E 13 N 1 1 0P TRAN 61m 1 m PLOT TRAN U 1 END x 0 728ms y 1 082V Figure 1 12 A screen shot of the netlist from the example input file and plots of nodes 1 and 2 taken using LTSPICE This lab is no way intended to be an LTSPICE or PSPICE manual This introduction only covers the basics that a student will need to run LTSPICE and PSPICE Other published material such as the ones in the reference reading on SPICE should be consulted for a better understa
14. g signals Amplitude sec Vo Va Jj p t t Jip AANA IAA VY V VM ri oe frequency Figure 1 2 ASIN wave created in SPICE Amplitude volts PW V1 t t T t time sec Amplitude volts t1 v1 a 1 4 A piecewise linear signal created in SPICE Dependant Sources Generic statement Ename n n p p A Example Eone 2 3 1 0 50 There are four nodes in the dependant source command The first two nodes of the voltage controlled voltage source VCVS n and n represent the node numbers for the positive and negative ports of the output The second set of node numbers represents the positive and negative nodes of source s reference voltage The gain of the VCVS is indicated by the value of A In the example the controlling or reference voltage of the VCVS is between nodes 1 and 0 while it has a gain of 50 The output of the VCVS is connected between nodes 2 and 3 The value of the output is dependent on the controlling voltage by a factor of the gain When dealing with units there are certain scale factor abbreviations that HSPICE will recognize The acceptable abbreviations for HSPICE are listed in table 1 3 Table 1 3 Scaling abbreviations Spice Abbreviation Metric Prefix Multiplication factor SPICE does not require you to label the units however here are the acceptable unit abbreviations Table 1 4 Unit abbreviations Spice Abbreviation Caution If not caught SPICE ha
15. ition This means that the capacitor has an initial voltage at time equal to zero If the IC initial condition part is left off SPICE will assume that the initial voltage on the capacitor is zero volts Caution Remember the unit problems with capacitors stated earlier Inductor Generic Lname n n value C initial condition Example Lfeedback 50 0 1 The inductor is modeled similar to the capacitor except the initial condition is in terms of current as opposed to voltage This particular inductor has a OA initial condition Active elements The three basic active elements needed for this class are the diode BJT and the MOSFET The element statements for active devices are really similar to passive The fundamental difference is that the BJT and MOSFET are three and four terminal devices respectively The physical characteristics can also be a little more complicated Other than that active elements follow the same basic element statement format The first letter identifies the device type the next three statements are for the node numbers only two in the case of the diode and the last part of the statement contains the physical characteristics Since active devices have complicated physical characteristics a Model Statement is used An example of a diode BJT and MOSFET are all show below To better illustrate this technique they will have an accompanying explanation Diode Dname Figure 1 6 A schematic symbol
16. nalysis request statement is done below LTspice only lets the user have one analysis type work for each simulation Therefore if you want to have multiple analysis types for a given circuit you will need to simulate it multiple times If you want to view the operating point for an analysis this is saved in a file named filename op raw DC operating point requested OP DC sweep Generic statement DC source_name starting_value ending_value step_value Example DC power OV 5V 0 1V A DC sweep is done for many reasons For example you would use a DC sweep if you wanted to see the different responses of a circuit for different biasing conditions In the example the DC analysis command instructs the source named power in the circuit to start at OV and increase its values by increments of 0 1V until it reaches a value of 5V then it stops You would then use a specific output request to see the response this will be discussed later AC frequency response Generic AC type number_of_points frequency_start frequency_stop There are three different types of AC frequency responses The difference deals with how the points are taken You can specify the following types DEC points are spaced logarithmically by decade OCT points are spaced logarithmically by octave or LIN points are linear spaced Example of the three different types AC DEC 100 2k 1e6 AC OCT 1000 2k 1e6 AC LIN 50 500 550 The AC command d
17. nding Reference Reading 1 Gordon W Roberts and Adel S Sedra SPICE Second edition New York Oxford Press 1997 2 Marc E Herniter Schematic Capture with MicroSim Pspice Third edition Upper Saddle River New Jersey Prentice Hall 1998 3 LTSPICE IV user manual http Itspice linear com software scad3 pdf 4 PSPICE user manual http www electronics lab com downloads schematic 013 tutorial PSPCREF pdf Lab exercises 1 The topology below is the circuit from the first homework problem 1 Verify your results from problem 1 part h of the homework using SPICE Please turn in all graphs that prove the results you obtained Be sure to label the graphs to indicate what Av Q Rout Tec and 3 4g are Last of all turn in your SPICE netlist Figure 1 13 The circuit used for homework 1 problem 1 2 The topology below is the circuit from the first homework problem 2 Please verify the exact results you found in problem 2 part h using SPICE Please turn in all graphs that prove the results you obtained Also note that you must label graphs to indicate what Rin Rout 3dB bandwidth or Av O are Last of all please turn in your SPICE netlist R r Reas mal oO M Y pI r ZC bg Figure 1 14 The circuit used for homework 1 problem 2 E oe _ Chitput Guiput V R a Ra T Y R n Ry 7 _ R nS eee III La a a g Figure 1 15 The circuit use
18. oes not need the name of the source An AC source is the only source that allows for this type of analysis so HSPICE will implement this analysis to the AC source in the circuit automatically The first AC command depicts a statement that performs a frequency sweep that takes 100 points per decade The analysis starts at 2kHz and ends at 1MHz The other two statements follow the same format Following the AC command are statements that indicates the way points are taken and the number of points taken respectively Finally the starting and ending frequencies are listed Transient response Generic TRAN step_time stop_time Example TRAN 10n 10m This example simulates the circuit for 10ms and takes data points every 10ns The TRAN analysis is preformed when the response of the circuit with time is desired For example a transient response request would be used if you wanted to see the time it takes a capacitor to charge or discharge Caution For correct data collection make sure that the smallest step time in the transient command is equal to or smaller then the fastest change in your signal You must also make sure that the transient time complements the source or you will not be able to see the simulated results Transfer Function Generic TF V node source Example TF V out Vin TF V 2 1 Vin TF I Rout Vin These examples all compute the DC small signal transfer functions for different outputs with r
19. of a diode a represents the anode terminal c represents the cathode terminal Generic under device section Dname ac model_name Under Model Statement section Model model_name D certain parameter 1 value certain parameter 2 value etc 1OExample under device section Drec 2 3 fermi under Model Statement section Model fermi D Is 150pA n 1 2 This example is of a diode named rec It is connected between nodes number 2 and 3 This diode references its physical characteristics from a Model statement called fermi In this particular example the only parameters dictated to Spice are Is and n More parameters can be specified if desired Table 1 5 is a list of typical parameters specified for a diode and the default setting for each Reverse bias breakdown voltage Reverse bias breakdown current BJT NPN E Figure 1 7 Schematic symbol for BJTs B is the Base terminal C is the Collector terminal E is the emitter terminal The BJT element statement is very similar to the diode The main difference is that it has three terminals instead of two Other than that the structure of the statement is very similar An example of a NPN is done below Generic under device section Qname C B E model_name under Model Statement section Model model_name NPN certain parameter 1 value certain parameter 2 value etc Example under device section Q1 3 145 normal under Mod
20. ors and Functions w Digital V Voltages V Currents V Power Noise H2 Alias Names Subeircuit Nodes 9 variables listed Full List Trace Expression Figure 1 10 Window that appears in PSPICE when adding traces From this window you can add traces by selecting them and clicking OK Trace Expressions When adding traces in LTSPICE or PSPICE you can add expressions of traces This is very helpful when you want to see mathematical properties of node voltages and element currents Expressions can be written in the Trace Expression line in the above two windows when traces are added The following table lists the functions available for real data in LTSPICE Table 1 10 List of allowed functions for real data in LTSPICE Function Name Absolute value of x acos Arc cosine of x Description arccos x Synonym for acos acosh x Arc hyperbolic cosine Arc sine arcsin x Synonym for sin Arc hyperbolic sine atan x Arc tangent of x arctan x ym for atan atan2 y xX Four quadrant arc tangent of y x atanh x Arc hyperbolic tangent 1 if x gt 5 else O Integer equal or greater than x Cosine of x Hyperbolic cosine of x Finite difference based derivative e to the xX floor x Integer equal to or less than x hypot x y sgrt x 3 y 2 1f x y z If x gt 5 then y else z Convert x to integer 0 1 gt 5 else 1 limit
21. put statements that may be used to measure voltage voltage difference or current in a circuit Table 1 9 Data collection methods for print and plot commands Measuring output form Voltage at a specific node Vinode number Voltage difference between two nodes V node number node number2 Current through any element l Element name Some examples are done below Probe For Pspice only Generic Probe output Example Probe V 1 I Rout Probe The first example will write the results of the voltage at node 1 and the current through the resistor named out The second example will write all the node voltages and element currents in the circuit These results can be viewed with the wave viewer provided by PSPICE Print For Pspice only Generic PRINT type output Example PRINT DC V out This example will print the values of the node voltage called out from the DC sweep in a table in the output file Plot For Pspice only Generic Plot type output Example PLOT AC I R10 This example will plot the values of the current through the resistor called 10 from the ac sweep in the output file NOTE Plot and Print are methods for viewing results from a SPICE analysis in the output file This is the standard method for an HSPICE netlist However PSPICE and LTSPICE have a wave viewer that allows the user to plot the results from analysis These are much better for viewing purposes Thus
22. r LTSPICE and PSPICE are provided in the references section at the end of this lab LTSPICE and PSPICE provide the user with the ability to generate SPICE netlists via schematics While this tool is very useful this lab will still focus on how to write a good SPICE netlist as opposed to create a schematic This is because the ability to read and write a SPICE netlist is very valuable for electrical engineers One drawback of PSPICE is that its free demo version only allows the user to have up to 10 of the same type of transistor However since the labs in OHE230 only have PSPICE students will have to use it during their labs First time LTSPICE setup on your computer 1 Got to Linear Technology s website to download the exe http www linear com designtools software 2 Scroll down to where it says LTspice IV To the right click on the link that says Download LT spice IV You do not need to register for a MyLinear account just click on No thanks just download the software 3 After the download is complete run the exe file that you downloaded LTspiceIV exe Accept the conditions and click Install Now 4 You are now ready to run LTspice First time PSPICE setup on your computer 1 Got to Cadence s website to download the exe http www cadence com products orcad pages downloads aspx installer 2 Click on PSPICE Schematics Installer 3 You will need to fill out a form The only field that
23. s a really fatal flaw If you notice the abbreviation for Farads and femto are both F This can be a cause for real heart burn If you were to label your capacitance value 1F thinking this represents one farad you would soon find out that spice interprets this as 1 femto farad 1e 15 Farads To be safe just leave the units off when dealing with capacitance Another common mistake is mixing up mega with milli For example if you want to make a resistance of 1 mega ohms and use m instead of meg you will create a resistance of 1 milli ohms Passive elements Passive element statements are very similar to DC sources The first letter indicates the passive element that is being used The letters for a standard resistor capacitor and inductor are listed in table 1 1 A schematic diagram of each is shown below The schematic diagrams accompanied by a generic statement an example statement and a brief explanation name nt FF n Figure 1 5 Schematic symbols of a resistor capacitor and inductor Resistor Generic Rname n n value Example R15 0 10k The example depicts a resistor named 1 which is connected between nodes 5 and 0 ground It has a value of 10k Ohms Capacitor Generic Cname n n value IC initial condition Example Cload 50 0 10u C 0 5V This example is a capacitor named load connected at nodes 50 and 0 ground and it is 10 microfarads This capacitor also has a 0 5V initial cond
24. ulse that should happen Leave it as zero if you want ongoing pulses THIS IS FOR LTSPICE ONLY This element statement describes a sinusoidal signal named input at it is connected between nodes 2 and 1 The signal has an initial voltage of OV and a magnitude of 5V It has a frequency of 1OkHz and a time delay of 5milliseconds The signal has no damping factor If the statement does not contain values for td damping phase advance or ncycles then spice assumes a value of zero for all PULSE Generic statement Vname n n PULSE V1 V2 td tr tf PW T ncycles LTSPICE only NOTE tr and tf are swapped when declaring a pulse in PSPICE Example V50 15 0 PULSE 2 5 0 2e 3 4e 5 5 10 0 VI is the lower voltage value V2 is the upper voltage value td is the time delay in seconds tr is the time in seconds it takes for the pulse to rise tf is the time in seconds it takes for the pulse to fall PW is the pulse width of the peak value or the time the pulse remains at the upper voltage value in seconds T is the time of one pulse period in seconds ncycles is the number of cycles of the pulse that should happen Leave it as zero if you want ongoing pulses THIS IS FOR LTSPICE ONLY The example details a pulse named 50 It is connected to nodes 15 and 0 The pulse has a lower voltage value of 2V and an upper value of 5V The time delay is zero seconds while it takes 2ms and 40us for the pulse to rise and fall respectively
25. x y z Intermediate value of x y and z Natural logarithm of x Alternate syntax for ln log10 x Base 10 logarithm max x y The greater of or Y min x The smaller of x or y pow x y pwr x y abs x y rand x Random number between 0 and 1 depending on the integer value of x random x Similar to rand but smoothly transitions between values round x Nearest integer to x Sign of Sine of x sinh x Hyperbolic sine of sqrt x Square root of x table z a b c d Interpolate a value for x based on a look up table given as a set of pairs of points Tangent of Hyperbolic tangent of x Unit step else 0 white x Random number between 5 and 5 smoothly transitions between values even more smoothly than random For complex data the functions atan2 sgnQ uQ bufQ invQ urampQ intQ floorQ ceilQ rand min limit if and table are not available The functions Re x and Im x are available for complex data and return a complex number with the real part equal to the real or imaginary part of the argument respectively and the imaginary part equal to zero The functions Ph x and Mag x are also available for complex data and return a complex number with the real part equal to the phase angle or magnitude of the argument respectively and the imaginary part equal to zero The function conj x is also available for complex data and returns the compl

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