Problem 7.4 - The Exponential (EXP function) Waveform
*
* NOTE: This is a two-part problem.
* Part 1: Use the EXP waveform function to generate v(t) = 5exp(-t).
* Use the .TRAN command with a time interval 0 < t < 5 seconds.
* Use .PROBE to display a graph of v(t) (the node voltage V(1)).
*
* Part 2: CHALLENGE PROBLEM! Write a PSpice circuit data file to
* generate the delayed exponential pulse, v(t)=5exp(-(t-2))u(t-2).
* This function has the value 0 from t=0 to t=2 seconds. It jumps
* to 5 volts at t=2, then decays exponentially to zero volts final
* value with a time constant of 1 second. (See the problem state-
* ment in the manual for a helpful hint on approximating the zero
* rise time of the function at t=2 seconds.)
*
* NOTES ON THE EXP FUNCTION: (See Appendix A for additional information.)
* 1. The EXP function describes an exponential waveform in terms of
* its initial value, asymptotic final value, delay from t=0 to the
* start of the rising waveform, the rise time constant, the delay
* from t=0 to the start of the falling waveform, and the fall time
* constant.
* 2. The "rise time" may describe a falling waveform, as in this
* problem. That is, if the initial value is higher than the final
* value, the first time constant that is entered (the "rise" time
* constant) describes the exponentially decreasing waveform shape.
* 3. At least the first five parameters of the exponential waveform
* function must be entered: the default value of the time delay to
* the beginning of the falling waveform is TSTEP (the first number
* in the .TRAN command statement). If only one segment of the
* waveform is desired, either rising or falling, then the fall time
* delay parameter should be set equal to or greater than the .TRAN
* analysis period.
*
.OPT NOPAGE
V1 1 0 EXP(5 0 TD TCR TF) ;Enter the correct values for the
; time delay from t=0 to the start
; of the waveform (TD), the "rise" time constant (TCR),
; and the end time of the rising waveform (TF). This
; will be the final time of the .TRAN analysis period,
; in this case, since there is second segment of the
; waveform in this problem.
; NOTE: An excellent problem for the curious is
; to let TF be less than the .TRAN period and
; note the automatic generation of a second
; exponential segment of the waveform. Control
; of the shape of the second segment is by a
; "fall" time constant entered following TF.
; See Section A.3.3.3 for more information.
R1 1 2 1K
R2 2 0 3K
.TRAN .2 5 0 .05
.PROBE
.END
* Problem 7.4, Part 2. CHALLENGE PROBLEM! The Exponential (EXP) Waveform
* *
* Write a PSpice data file to generate the delayed exponential pulse, *
* v(t) = 5*EXP(-(t-2))u(t-2). See the problem statement for helpful *
* hints on obtaining this waveform, which has the value zero from t=0 *
* to t=2 seconds, jumps to 5 volts at t=2, and decays exponentially *
* to zero volts final value with a time constant of 1 second. * *
* *
* * * * * * * * * * * * * * * * * * ** * * * * * * * * * * * * * * * * * * *