This is an example of a SPICE input file that will calculate the DC Node voltages, the Thevenin Equivalent Circuit and also sweep the input voltage source.
Input file: (the lines starting with a "*" are comment lines and are inserted for clarity only).
DC Sweep:
a: v(1,2)
b: v(2,4)
+0:1 = 10.0000 0:2 = 9.7275 0:3 = 9.4340 +0:4 = 0.
**** voltage sources
Currents in Voltage sources:
**** current-controlled current sources
Input file: (the lines starting with a "*" are comment lines and are inserted for clarity only).
- Spice Example: DC Sweep, .TF, .OT analysis* * We are interested in finding the following characteristics: * 1. Node voltages v12, v2 and current i4 when vin=10V * 2. Thevenin equivalent voltage and resistance, seen * at the output terminals v(3,0) * 3. Sweep the input from 0 to 20V in steps of 2V and plot * the voltages v12, v2, vo and the current i4. * ------------------------------------------------------ VIN 1 0 DC 10 F1 0 3 VMEAS 0.5 VMEAS 4 0 DC 0 *VMEAS is a 0V source to measure i4 R1 1 2 1K R2 2 3 10K R3 1 3 15K R4 2 4 40K R5 3 0 50K .OP * -------------------------------------------------- * The operating point .OP command will tell Spice * print all DC node voltages, currents through voltage * sources and voltages over current sources. * -------------------------------------------------- .TF V(3,0) VIN * -------------------------------------------------- * The .TF statement tells Spice to calcuate the ratio of * Vout/Vin and the resistance seen at the terminals of * Vout=V(0,3) and Vin (corresponding to the output and * input resistances). This statement is used to calculate * the Thevenin equivalent circuit. * -------------------------------------------------- .DC VIN 0 20 2 * -------------------------------------------------- * The .DC statement instructs Spice to sweep the voltage source * Vin from 0 to 20 V in steps of 2V. * -------------------------------------------------- .PLOT DC V(1,2) V(2,4) .PLOT DC I(VMEAS) * -------------------------------------------------- * The above Plot statement instruct Spice to plot the * node voltages and current in the Vmeas voltage source, * obtained as a results of the DC sweep. * -------------------------------------------------- .END
DC Sweep:
a: v(1,2)
b: v(2,4)
volt v(1,2) (ab ) 0. 5.0000 10.0000 15.0000 20.0000 + + + + + 0. 0. -2------+------+------+------+------+------+------+------+- 2.0000 54.507m a b + + + + + + + + 4.0000 109.015m a + b + + + + + + + 6.0000 163.522m a + + b + + + + + + 8.0000 218.029m +a + + +b + + + + + 10.0000 272.537m +a + + + b+ + + + + 12.0000 327.044m +a + + + + b + + + + 14.0000 381.551m +a + + + + + b + + + 16.0000 436.059m +a + + + + + + b + + 18.0000 490.566m +a + + + + + + b + 20.0000 545.073m-+-a----+------+------+------+------+------+------+----b-+- + + + + + volt i(vmeas) (a ) 0. 200.0000u 400.0000u 600.0000u 800.0000u + + + + + 0. 0. -a------+------+------+------+------+------+------+------+- 2.0000 48.637u + a + + + + + + + + 4.0000 97.275u + a + + + + + + + 6.0000 145.912u + + a + + + + + + + 8.0000 194.549u + + a + + + + + + 10.0000 243.187u + + + a + + + + + + 12.0000 291.824u + + + a+ + + + + + 14.0000 340.461u + + + + a + + + + + 16.0000 389.099u + + + + a+ + + + + 18.0000 437.736u + + + + + a + + + + 20.0000 486.373u-+------+------+------+------+-----a+------+------+------+- + + + + +***** operating point status is all simulation time is 0. node =voltage node =voltage node =voltage
+0:1 = 10.0000 0:2 = 9.7275 0:3 = 9.4340 +0:4 = 0.
**** voltage sources
Currents in Voltage sources:
- element 0:vin 0:vmeas volts 10.0000 0. current -310.2725u 243.1866u power 3.1027m 0. total voltage source power dissipation= 3.1027m watts
**** current-controlled current sources
- element 0:f1 current 121.5933u
- v(3)/vin = 943.3962m input resistance at vin = 32.2297k output resistance at v(3) = 5.6604k
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