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### Exponential

General Form:
exp(v1 v2 [td1 tau1 td2 tau2])
Example:
vin 3 0 exp(-4 -1 2ns 30ns 60ns 40ns)

This function can be called as texp to avoid possible conflict with the exp math function.

 parameter description default value units v1 initial value volts or amps v2 pulsed value volts or amps td1 rise delay time 0.0 seconds tau1 rise time constant tstep seconds td2 fall delay time td1 + tstep seconds tau2 fall time constant tstep seconds

The shape of the waveform is described by the following table:

 time value 0 v1 td1 v1 + (v2- v1)(1 - exp(- (time- td1)/tau1)) td2 v1 + (v2- v1)(1 - exp(- (time- td1)/tau1)) + (v1- v2)(1 - exp(- (time- td2)/tau2))

This function applies only to transient analysis, where time is the running variable. When referring to default values, tstep is the printing increment and tstop is the final time in transient analysis, see 2.7.10 for explanation. The argument count is used to distinguish this function from the math function of the same name.

If this function is used bare and not part of an expression in a voltage or current source, then the general source instance parameters prm1 etc. map as below. It is possible to read and alter these values using the special vector @device[param] construct, or with the alter and sweep commands. However, there is no sanity checking so bad numbers can cause wild behavior or worse.

 prm1 v1 prm2 v2 prm3 td1 prm4 tau1 prm5 td2 prm6 tau2

Next: Gaussian Random Up: Tran Functions Previous: Tran Functions   Contents   Index
Stephen R. Whiteley 2022-09-18