IPULSE - Pulse Current Source Model

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Modified by Phil Loughhead on Mar 4, 2014

Model Kind

Current Source

Model Sub-Kind

Pulse

SPICE Prefix

I

SPICE Netlist Template Format

@DESIGNATOR %1 %2 ?"DC MAGNITUDE"|DC @"DC MAGNITUDE"| PULSE(?"INITIAL VALUE"/&"INITIAL VALUE"//0/ ?"PULSED VALUE"/&"PULSED VALUE"//5/ ?"TIME DELAY"/&"TIME DELAY"//0/ ?"RISE TIME"/&"RISE TIME"//4U/ ?"FALL TIME"/&"FALL TIME"//1U/ ?"PULSE WIDTH"/&"PULSE WIDTH"//0/ ?PERIOD/&PERIOD//5U/ &PHASE) #"AC MAGNITUDE"|AC @"AC MAGNITUDE"| @"AC PHASE"

Parameters (definable at component level)

The following component-level parameters are definable for this model type and are listed on the Parameters tab of the Sim Model dialog. To access this dialog, simply double-click on the entry for the simulation model link in the Models region of the Component Properties dialog.

DC Magnitude

DC offset used in an Operating Point Analysis. (Default = 0).

AC Magnitude

the magnitude of the source when used in an AC Small Signal Analysis. (Default = 1).

AC Phase

the phase of the source when used in an AC Small Signal Analysis. (Default = 0).

Initial Value

current amplitude at time zero (in Amps). (Default = 0).

Pulsed Value

maximum amplitude of the output swing (in Amps). (Default = 5).

Time Delay

delay before the source changes from Initial current value to Pulsed current value (in seconds).

Rise Time

the time it takes to rise from Initial current value to Pulsed current value (in seconds). Must be > 0. (Default = 4u).

Fall Time

the time it takes to fall from Pulsed current value back to the Initial current value (in seconds). Must be > 0. (Default = 1u).

Pulse Width

the time that the source remains at the Pulsed current amplitude (in seconds). (Default = 0).

Period

the time between the start of the first pulse and the start of the second pulse (in seconds). (Default = 5u).

Phase

phase shift of the waveform at time zero (in Degrees).

Notes

  1. The image below shows an example waveform produced by a periodic-pulse current source (connected to a 1Ohm load). The Pulse Width has been set to 5u, the Period has been set to 20u. All other parameters have been left at their default values:

  1. The shape of the waveform is described as follows:

I(t0) = IIV
I(tTD) = IIV
I(tTD + tRT) = IPV
I(tTD + tRT + tPW) = IPV
I(tTD + tRT + tPW + tFT) = IIV
I(tSTOP) = IIV

where,

  • t is an instance of time
  • IIV is the initial value of the current
  • IPV is the pulsed value of the current
  • tTD is the Time Delay
  • tRT is the Rise Time
  • tPW is the Pulse Width and
  • tFT is the Fall Time
  1. The value for the current at intermediate values of time is calculated using linear interpolation.
  2. The simulation-ready pulse current source component (IPULSE) can be found in the Simulation Sources integrated library (\Library\Simulation\Simulation Sources.IntLib).

Examples

Consider the pulse current source in the above image, with the following characteristics:

  • Pin1 (positive) is connected to net GND
  • Pin2 (negative) is connected to net CP
  • Designator is ICP
  • Pulsed Value = 5m
  • Time Delay = 0
  • Rise Time = 1u
  • Pulse Width = 500u
  • Period = 1000u
  • All other parameters for the model are left at their default values.

The entry in the SPICE netlist would be:

*Schematic Netlist: 
ICP 0 CP DC 0 PULSE(0 5m 0 1u 1u 500u 1000u) AC 1 0

 

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