Problem 5.6 - Thevenin Equivalent Circuit with Negative Resistance
*
* The circuit for this problem is from textbook Chap. 5, Problem 15.
*
* NOTE: This is a three-part problem:
* 1. Use PSpice to calculate the open circuit voltage V(1,6).
* 2. Add a 1-ampere current source at terminals 1,6 to determine
* the output (Thevenin) resistance. REMEMBER that all independent
* sources must be reduced to zero for this calculation.
* Hand-calculate the Thevenin equivalent circuit resistance.
* Be careful of voltage and current polarities in this case.
* 3. Connect a variable load resistance to the circuit. Use PROBE
* to obtain a graph of the power delivered to the load resistance.
* Can you explain the significance of the result in this problem,
* wherein "negative power" is delivered to the load?
*
.OPT NUMDGT=5 NOPAGE
I1 2 3 DC ??? ; Enter correct value of current source.
I2 4 5 DC 5
V1 6 5 DC ??? ; Enter correct value of voltage source.
G1 0 4 ??? ??? 2 ; Enter + and - control voltage nodes.
H1 1 0 VS 3
VS 31 3 DC 0 ; Node added for zero-volt source to
; measure the control current iy. Draw
; this source on the circuit diagram,
; using the node data for R34 below.
R12 1 2 1
R2 2 0 3
R3 3 0 6
R34 31 4 5
R5 5 0 3
R6 6 0 6
.DC V1 ; Complete the .DC sweep command statement.
.PRINT DC V(1) V(6) V(1,6)
.END
Problem 5.6, Part 2. Thevenin Equivalent Circuit with Negative Resistance
*
* Determine Thevenin resistance using a 1-amp current source at the
* load terminals. Polarity of source and voltage is important!
* REDUCE ALL INDEPENDENT VOLTAGE AND CURRENT SOURCES TO ZERO.
*
.OPT NUMDGT=5 NOPAGE
I1 2 3 DC ??? ; Enter correct value of current source.
I2 4 5 DC ???
V1 6 5 DC ??? ; Enter correct value of voltage source.
G1 0 4 ??? ??? 2 ; Enter + and - control voltage nodes.
H1 1 0 VS 3
VS 31 3 DC 0 ; Node added for zero-volt source.
IT ??? ??? DC 1 ; Complete the device statement for the
; 1-amp test current source used to
; determine the Thevenin resistance.
R12 1 2 1
R2 2 0 3
R3 3 0 6
R34 31 4 5
R5 5 0 3
R6 6 0 6
.DC IT 1 1 1
.PRINT DC V(1) V(6) V(1,6)
.END
Problem 5.6, Part 3. Thevenin Equivalent Circuit with Negative Resistance
*
* Connect a variable load resistance. Sweep the variable load
* resistance through the Thevenin resistance value. Compare
* the voltage V(1,6) at RLOAD = -10 with the Thevenin voltage.
* Use PROBE to graph the power delivered to the load resistance.
*
.OPT NUMDGT=5 NOPAGE
I1 2 3 DC ??? ; Enter correct value of current source.
I2 4 5 DC 5
V1 6 5 DC ??? ; Enter correct value of voltage source.
G1 0 4 ??? ??? 2 ; Enter + and - control voltage nodes.
H1 1 0 VS 3
VS 31 3 DC 0 ; Node added for zero-volt source.
R12 1 2 1
R2 2 0 3
R3 3 0 6
R34 31 4 5
R5 5 0 3
R6 6 0 6
R16 1 6 RLOAD 1
.MODEL RLOAD RES(R=-2)
.DC RES RLOAD(R) -2 -20 -1
.PROBE ; Graph V(1,6)*I(R16) for the power curve.
.PRINT DC V(1) V(6) V(1,6)
.END