Problem 9.1 - Complete Response of an RLC Circuit to an Exponential Input
*
* The circuit for this problem is similar to textbook Example 9.2,
* with the time constants adjusted.
* Use exponential (EXP) source representing the time domain function
* i(t)=40exp(-3t). Use PROBE to display the response of the circuit.
* The waveform that will be displayed is the complete response,
* consisting of the transient (natural) response of the circuit plus
* the steady-state (forced) response due to the excitation.
* Add the expression for the steady-state response to the PROBE graph
* and determine the approximate time in seconds before the transient
* has "died out" and the output waveform is equal to the steady-state
* response. How many time constants of the input exponential waveform
* does this time represent?
*
* NOTE: When you add an expression to be plotted by PROBE you must
* use the full name of the horizontal axis variable (TIME, FREQUENCY).
*
* .TRAN analysis is necessary because of the source type.
* Use initial conditions (UIC) is necessary for correct response with
* this waveform, which is discontinuous at the origin. The complete
* response is v(t)=-.504exp(-3t)-2.353exp(-20t)+2.857exp(-10t).
*
* ===> After the first program run, edit the program to change R1 to 1/30
* ohm and L1 to .01 henry. The steady state solution for this circuit
* is v1p(t)=-4.29exp(-3t). Add the graph of the steady-state response
* to the circuit complete response graph. Answer the questions as for
* Part 1.
*
* ===> Suggestion for "PSpice experiment": What is the value of resistance
* R1 for critical damping? What is the response of the circuit when
* the resistance is greater than the value for critical damping. Try
* to estimate the response when the resistance is 0.2 ohms, for
* example. Then edit and run the program to check yourself.
*
.OPT NOPAGE NOBIAS
IS 0 1 EXP(40 ??? ??? .33333 ??) ; Enter the EXP source parameters.
; Note that this waveform is
; similar to one in the Chapter 7
; problem section, where the "rise"
; of the waveform is from a positive
; voltage to 0 volts final value.
R1 1 0 .016667
L1 1 0 .0025
C1 1 0 2
.TRAN .05 2 0 .02 UIC ; The two-second analysis period of
; the .TRAN function is approximately
; six time constants of the source
; waveform. The steady-state (forced)
; response should have gone to zero
; along with the input signal by the
; end of the two-second period.
.PROBE
.END
* Prob 9.1, Part 2. Complete Response of an RLC Circuit to Exponential Input
*
* Re-write the circuit description file used above, except with the
* device values R=1/30 and L=0.01 to agree with the textbook example.
*