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SPICE USING LTSPICE DR. ASLAN TEXAS STATE UNIVERSITY

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OUTLINE Introduction to SPICE DC Analysis Transient Analysis AC Analysis Subcircuits Optimization Power Measurement

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INTRODUCTION TO SPICE Simulation Program with Integrated Circuit Emphasis Developed in 1970’s at Berkeley Many commercial versions are available HSPICE is a robust industry standard Has many enhancements that we will use Written in FORTRAN for punch-card machines Circuits elements are called cards Complete description is called a SPICE deck

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WRITING SPICE DECKS Writing a SPICE deck is like writing a good program Plan: sketch schematic on paper or in editor Modify existing decks whenever possible Code: strive for clarity Start with name, , date, purpose Generously comment Test: Predict what results should be Compare with actual Garbage In, Garbage Out!

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SOME FACTS AND RULES ABOUT SPICE Spice is not case sensitive. Rsource and RsOuRcE and RSOURCE are equivelent. All element names must be unique. You can't have two capacitors that both are named “C1”. The first line in the data file is used as a title. Spice will ignore this line as circuit data. Put your name and title. There must be a node designated "0" (Zero). This is the reference node against which all voltages are calculated. Each node must have at least two elements attached to it. The last line in any data file must be ".END" (a period followed by the word "end.") All lines that are not blank (except for the title line) must have a character in column 1, the leftmost position on the line. Use "*" (an asterisk) in column 1 in order to create a comment line. Use "+" (plus sign) in column 1 in order to continue the previous line (for better readability of very long lines). Use "." (period) in column 1 followed by the rest of the "dot command" to pass special instructions to the program. Use the designated letter for a part in column 1 followed by the rest of the name for that part (no spaces in the part name). Use "whitespace" (spaces or tabs) to separate data fields on a line. Use ";" (semicolon) to terminate data on a line if you wish to add commentary information on that same line.

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SPICE ELEMENTS

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UNITS LetterUnitMagnitude aatto ffempto ppico nnano10 -9 umicro10 -6 mmili10 -3 kkilo10 3 xmega10 6 ggiga10 9 Ex: 100 femptofarad capacitor = 100fF, 100f, 100e-15

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SOURCES - DC DC Source Vname N1 N2 Type Value Iname N1 N2 Type Value Vs10DC20V Is04DC50MA Va 4 2 DC 16.0V; "V" after "16.0" is optional vs qe qcdc 24m ; "QE" is +node & "qc" is -node VWX k ; "dc" not really needed vwx DC -1.8E4 ; same as above Vdep DC 0V ; V-source used as ammeter

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SOURCES - AC DC Source Vname n+ n-Type ValuePhase (Deg) Iname n+ n-Type ValuePhase (Deg) Vac 4 1 AC 120V 30 Vba 2 5 AC 240 ; phase angle 0 degrees Ix 3 6 AC 10.0A -45 ; phase angle -45 degrees Isv 12 9 AC 25mA ; 25 0 degrees

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SOURCES – DEPENDENT Voltage controlled voltage source: Ename n+ n- nc+ nc- Voltage Gain Value Ebar ; gain is 24 efix ; same as above Ellen Voltage controlled current source: Gname n+ n- nc+ nc- Value Glab G E-2 Grad Grad ; same as above Grad ; etc.

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SOURCES – DEPENDENT (CONT.) Current controlled voltage source: Hname N1 N2 Vcontrol Value Hvx Vhx 50.0 Vhx DC 0V ; controls Hvx Hab 10 0 V V DC 0V ; controls Hab HAL Vuse 10.0 Vuse 3 5 DC 20V ; actual voltage source Current controlled current source: Fname N1 N2 Vcontrol Value Ftrn Vctl 50.0 Vclt DC 0V ; controls Ftrn Fcur Vx 20.0 Vx DC 0V ; controls Fcur F3 2 0 V V1 3 1 DC 0V ; controls F3

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SOURCES – PULSE Vname n+ n- Pulse(V1 V2 Td Tr Tf Tw Period) V1: Initial voltage V2: Peak voltage Td: Initial delay time Tr: Rise time; Tf: Fall time; Tw: Pulse width Period : Period. Vs 1 0 Pulse(0V 10V ) Vs 1 0 Pulse(0V 10V 0s 100ms 100ms 900ms 2s) Vs 1 0 Pulse( m 100m 900m 2)

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SOURCES – SINUSOIDAL Vname n+ n- Sin(Vo Va fr Td Theta phase) Vname = Vo + Va e [-Theta.(t - Td)] sin[2pi.fr (t - Td) + (Phase/360)] Vo: Offset voltage in volt. Va: Amplitude in volt. fr: The frequency in Hz. Td: Delay in seconds Theta : Damping factor per second Phase : Phase in degrees Vs 1 0 SIN(2V 5V 2Hz 200ms 2Hz 30d) VG 1 2 SIN( ) VG2 3 4 SIN( )

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SOURCES – PIECEWISE LINEAR SOURCE Vname n+ n- PWL(T1 V1 T2 V2 T3 V3...) T1: Time for the first point V1: Voltage for the first point T2: Time for the second point V2: Voltage for the second point Vgpwl 1 2 PWL(0 0 10U 5 100U 5 110U 0)

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CIRCUIT ANALYSIS -.OP.OP(Operating Point Analysis) Example_OP.CIR Vs 1 0 DC 20.0V ; note the node placements Ra k Rb k Rc k Is 3 2 DC 2.0mA ; note the node placements.OP.END If you need some values use.PRINT DC V(3,2) I(Ra)

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CIRCUIT ANALYSIS -.TRAN.TRANTransient Analysis * prt_stp t_max prt_dly max_stp.TRAN 20us 20ms 8ms 10us UIC 1. The following example performs and prints the transient analysis every 1 ns for 100 ns..TRAN 1NS 100NS 2. The following example performs the calculation every 10 ns for 1 µs; the initial DC operating point calculation is bypassed, and the nodal voltages specified in the.IC statement (or by IC parameters in element statements) are used to calculate initial conditions..TRAN 10NS 1US UIC

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CIRCUIT ANALYSIS -.TRAN Example_TRAN.cir Rp Lp 1 0 8mH IC=20A Cp mF IC=0V.TRAN 500us 100ms 0s 500us UIC.PROBE.END

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DATA TRANSFER TO MATLAB Assume I have the previous circuit Example_TRAN.cir. After you run Simulate now you can import your data to MATLAB for further analysis. In LTSpice go to File → Export Now you can open your MATLAB and relocate MATLAB directory where you saved “Example_ TRAN.txt” file. Highlight the data values (Transient analysis time will be added) Change the file name. Keep the extension (mace it.xls if you want to open in excel)

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DATA TRANSFER TO MATLAB (CONT.) Now you can open your MATLAB and relocate MATLAB directory where you saved “Example_ TRAN.txt” file. In MATLAB command window type >> load Example_TRAN.txt will create and error. This is due to forst line of the txt file. MATLAB cannot read that first line as data. Delete that line and save your file. Do not forget the order of the columns. (1 st Column is time, 2 nd I(Cp) and 3 rd one is I(Lp)) >> load Example_TRAN.txt In workspace of MATLAB you will see the loaded data. It hae 202 rows and 3 columns. Next step we will save the data as time, I(Cp) and I(Lp). Txt file xls file

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DATA TRANSFER TO MATLAB (CONT.) In workspace of MATLAB you will see the loaded data. It hae 202 rows and 3 columns. Next step we will save the data as time, I(Cp) and I(Lp). >> t=Example_TRAN(:,1); %This will save t as time variable >> I_Cp=Example_TRAN(:,2); %This will save I_Cp as time I(Cp) >> I_Lp=Example_TRAN(:,3); %This will save I_Lp as time I(Lp) Your work place shoul look like this Now we can plot these >> >> plot (t, I_Cp, t,I_Lp)

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CIRCUIT ANALYSIS -.AC * type #points start stop.AC LIN 160Hz 60Hz; <== what we want now..AC LIN ; <== a linear range sweep.AC DEC 20 1Hz 10kHz; <== a logarithmic range sweep.PRINT AC VM(30,9) VP(30,9); magnitude & angle of voltage.PRINT AC IR(Rx) II(Rx); real & imag. parts Rx current.PRINT AC VM(17) VP(17) VR(17) VI(17); the whole works on node 17

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CIRCUIT ANALYSIS -.AC Example_AC.cir Vs 1 0 AC 120V 0 Rg Lg mH Rm Lm mH Cx uF.AC LIN PRINT AC VM(3) VP(3) IM(Rm) IP(Rm) IM(Cx) IP(Cx).END

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CIRCUIT ANALYSIS -.AC First-order low-pass RC filter Vin 1 0 AC 1.0V Rf Cf uF.AC DEC Hz 100kHz.PROBE.END Second-Order High-Pass Filter Vin 1 0 AC 10V Rf CF uF Lf uH.AC DEC Hz 1MEG.PROBE.END

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SUBCIRCUITS * name nodelist.SUBCKT Example_ Iw DC 10A Ra Rb Rc Rd Re Rf Rg ENDS Subcircuit Example No. 1 * name nodelist.SUBCKT Example_ Iw DC 10A Ra Rb Rc Rd Re Rf Rg ENDS Vs 1 0 DC 50V Ra ; different from Ra above Rb ; different from Rb above Rc ; different from Rc above Rd ; different from Rd above * nodelist name X Example_1 X Example_1.END

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SUBCIRCUITS.SUBCKT OpAmp p_in n_in com out Ex int com p_in n_in 1e5 Ri p_in n_in 500k Ro int out 50.0.ENDS Subcircuit Example No. 2 - Inverting OpAmp.SUBCKT OpAmp p_in n_in com out Ex int com p_in n_in 1e5 Ri p_in n_in 500k Ro int out 50.0.ENDS Vg 1 0 DC 50mV Rg 1 2 5k Rf k RL k X OpAmp.END

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CIRCUIT ANALYSIS Voltage Divider Circuit VCC40DC12V R14110K R210RMOD 1.MODEL RMOD RES(R=1).STEP RES RMOD(R).1k, 15k, 1k RC432.7K RE201K Q1312Q2N3904 Model for 2N3904 NPN BJT (from Eval library in Pspice).model Q2N3904NPN(Is=6.734f Xti=3 Eg=1.11 Vaf=74.03 Bf=416.4 Ne= Ise=6.734f Ikf=66.78m Xtb=1.5 Br=.7371 Nc=2 Isc=0 Ikr=0 Rc=1 +Cjc=3.638p Mjc=.3085 Vjc=.75 Fc=.5 Cje=4.493p Mje=.2593 Vje=.75 +Tr=239.5n Tf=301.2p Itf=.4 Vtf=4 Xtf=2 Rb=10).OP.PRINT DC I(VCC) I(RC).END

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CIRCUIT ANALYSIS Voltage Divider Circuit VCC40DC12V R14110K R210RMOD 1.MODEL RMOD RES(R=1).STEP RES RMOD(R).1k, 15k, 1k RC432.7K RE201K Q1312Q2N3904.include bjt.lib.OP.PRINT DC I(VCC) I(RC).END

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THEVENIN’S THEOREM Thevenin Example No. 1 Vs 2 5 DC 100V Vc 2 3 DC 0V; controls Fx Fx 6 7 Vc 4.0; gain = 4 * n+ n- NC+ NC gain Ex ; gain = 3 R R R R R R MEG; satisfies PSpice * out_var input_source.TF V(1,0) Vs.END

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REFERENCES

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