P Spice allows the generation of dependent (or independent) voltage and current sources. Independent sources can be time variant .A nonlinear source can also be simulated by a polynomial.
The independent voltage and current sources that can be modeled by P Spice as follows:
1. Exponential
2. Pulse
3. Piecewise linear
4. Sinusoidal
5. Single- frequency frequency modulation
1. EXPONENTIAL SOURCE:
The symbol of exponential source is EXP. and the general form is
EXP (V1 V2 TRD TRC TFD TFC)
The waveform of an exponential waveform:
V1 and V2 must be specified by the user and can be either voltage or currents (TSTEP is the incrementing time during transient [.TRAN] analysis. In an exponential wave form, the voltage remains V1 for the first TRD seconds .Then the voltage raises exponentially from V1 to V2 with a fall time constant of TFC.
MODEL PARAMETERS OF EXPONENTIAL SOURCES
Name Meaning Units Default
V1 Initial Voltage Volts None
V2 Pulsed Voltage Volts None
TRD Rise Delay Time Seconds 0
TRC Rise Time Constant Seconds TSTEP
TFD Fall Delay Time Seconds TRD+TSTEP
TFC Fall Time Constant Seconds TSTEP
Typical Model Statements
V1=0,V2=1V
TRD=2ns , TRC=20ns
TFD=60ns , TFC=30ns
EXP ( 0 1 2NS 20NS 60NS 30NS)
The other sources will be discussed in future posts
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