Simulation Command - Revision history

Rsfjr at 21:06, 29 January 2014

2014-01-29T21:06:13Z

Lewispaul at 04:16, 7 July 2012

2012-07-07T04:16:43Z

Lewispaul: Add DISQUS for comments

2011-09-21T00:47:12Z

Add DISQUS for comments

Analogspiceman at 18:07, 20 August 2009

2009-08-20T18:07:51Z

Analogspiceman at 02:18, 18 August 2009

2009-08-18T02:18:41Z

Analogspiceman: /* Transient Analysis */

2009-08-18T01:35:05Z

‎Transient Analysis

Analogspiceman at 01:33, 18 August 2009

2009-08-18T01:33:53Z

Analogspiceman at 01:13, 18 August 2009

2009-08-18T01:13:28Z

Analogspiceman at 01:05, 18 August 2009

2009-08-18T01:05:06Z

Analogspiceman at 01:02, 18 August 2009

2009-08-18T01:02:32Z

@@ Line 3: / Line 3: @@
   .ac <oct, dec, lin> <Nsteps> <StartFreq> <EndFreq>
   .dc <srcnam> <Vstart> <Vstop> <Vincr> [<srcnam2> <Vstart2> <Vstop2> <Vincr2>]
-  .noise V(<out>[,<ref>]) <src> <oct, dec, lin> <Nsteps> <StartFreq> <EndFreq>
+  .noise V(<out>[,&lt;ref>]) <src> <oct, dec, lin> <Nsteps> <StartFreq> <EndFreq>
-  .tf V(<node>[, <ref>]) <source> '''''OR''''' I(<voltage source>) <source>
+  .tf V(<node>[, &lt;ref>]) <source> '''''OR''''' I(<voltage source>) <source>
   .op
 At the schematic level these commands may be entered directly as a [[SPICE Directive]] (''ctrl''-right-click on the text to edit) or may be entered via the drop down menu item: '''Simulate => Edit Simulation Cmd'''.
@@ Line 80: / Line 80: @@
 This is a frequency domain analysis that computes the noise due to Johnson, shot and flicker noise.&nbsp; The output data is noise spectral density per unit square root bandwidth.
-  Syntax: .noise V(<out>[,<ref>]) <src> <oct, dec, lin> <Nsteps> <StartFreq> <EndFreq>
+  Syntax: .noise V(<out>[,&lt;ref>]) <src> <oct, dec, lin> <Nsteps> <StartFreq> <EndFreq>
-V(<out>[,<ref>]) is the node at which the total output noise is calculated.&nbsp; It can be expressed as V(n1, n2) to represent the voltage between two nodes. <src> is the name of an independent source to which input noise is referred.&nbsp; <src> is the noiseless input signal.&nbsp; The parameters <oct, dec, lin>, <Nsteps>, <StartFreq>, and <EndFreq> define the frequency range of interest and resolution in the manner used in the .ac directive.
+V(<out>[,&lt;ref>]) is the node at which the total output noise is calculated.&nbsp; It can be expressed as V(n1, n2) to represent the voltage between two nodes. <src> is the name of an independent source to which input noise is referred.&nbsp; <src> is the noiseless input signal.&nbsp; The parameters <oct, dec, lin>, <Nsteps>, <StartFreq>, and <EndFreq> define the frequency range of interest and resolution in the manner used in the .ac directive.
 Output data trace V(onoise) is the noise spectral voltage density referenced to the node(s) specified as the output in the above syntax.&nbsp; If the input signal is given as a voltage source, then data trace V(inoise) is the input-referred noise voltage density.&nbsp; If the input is specified as a current source, then the data trace inoise is the noise referred to the input current source signal.&nbsp; The noise contribution of each component can be plotted.&nbsp; These contributions are referenced to the output.&nbsp; You can reference them to the input by dividing by the data trace "gain".
@@ Line 92: / Line 92: @@
 This is an analysis mode that finds the dc small signal transfer function of a node voltage or branch current due to small variations of an independent source.
-  Syntax: .tf V(<node>[, <ref>]) <source>
+  Syntax: .tf V(<node>[, &lt;ref>]) <source>
     OR    .tf I(<voltage source>) <source>
 Examples:

@@ Line 1: / Line 1: @@
-At the netlist level the '''Simulation Command''' is simply a line of text that begins with any of the following [[Dot Commands]]:
+At the netlist level the '''Simulation Command''' is simply a line of text that begins with any of the following Dot Commands:
   .tran <Tstep> <Tstop> [Tstart [dTmax]] [modifiers]
   .ac <oct, dec, lin> <Nsteps> <StartFreq> <EndFreq>

← Older revision		Revision as of 00:47, 21 September 2011
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	\| Pseudo Transient \|\| .opt pTranTau=0		\| Pseudo Transient \|\| .opt pTranTau=0
	\|}		\|}
		+
		+	{{#widget:DISQUS
		+	\|id=ltwiki
		+	\|uniqid={{PAGENAME}}
		+	\|url={{fullurl:{{PAGENAME}}}}
		+	}}

@@ Line 24: / Line 24: @@
 Perform a Nonlinear Transient Analysis.
-Perform a transient analysis.&nbsp; This is the most direct simulation of a circuit.&nbsp; It basically computes what happens when the circuit is powered up. Test signals are often applied as independent sources.
+This is a time domain analysis.&nbsp; Selected circuit signals may be displayed in the Waveform viewer as they are simulated, much like an oscilloscope on the bench.&nbsp; It basically computes what happens when the circuit is powered up and runs.&nbsp; Test signals are often applied as independent sources or may be taken from captured data stored on file.
   Syntax: .tran <Tstep> <Tstop> [Tstart [dTmax]] [modifiers]
     or    .tran <Tstop> [modifiers]
@@ Line 30: / Line 30: @@
 Several ''modifiers'' can be placed on the .tran line.
-*'''UIC:&nbsp;''' Use Initial Conditions.&nbsp; Skip the D.C. operating solution and use user-specified initial conditions.&nbsp; Normally, a dc operating point analysis is performed before starting the transient analysis.&nbsp; This directive suppresses this initialization.&nbsp; The initial conditions of some circuit elements can be can be specified on a per-instance basis.&nbsp; <b title="UIC is not a particularly recommended feature of SPICE.&nbsp; Skipping the DC operating point analysis leads to a nonphysical initial condition.&nbsp; For example, consider a voltage source connected in parallel to a capacitance.&nbsp; The node voltage is taken as zero if not specified.&nbsp; Then, in the first time step, an infinite current is required to charge the capacitor.&nbsp; The simulator cannot find a short enough time step to make the current non-singular, and a 'time step too small convergence fail' message will be issued.">Hover Here for Hint</b>
+*'''UIC:&nbsp;''' Use Initial Conditions.&nbsp; Skip the D.C. operating solution and use user-specified initial conditions.&nbsp; Normally, a dc operating point analysis is performed before starting the transient analysis.&nbsp; This directive suppresses this initialization.&nbsp; The initial conditions of some circuit elements can be can be specified on a per-instance basis.&nbsp; <font color="green"><b title="UIC is not a particularly recommended feature of SPICE.&nbsp; Skipping the DC operating point analysis may often lead to a nonphysical initial condition.&nbsp; For example, consider a voltage source connected in parallel to a capacitance.&nbsp; The node voltage is taken as zero if not specified.&nbsp; Then, in the first time step, an infinite current is required to charge the capacitor.&nbsp; The simulator cannot find a short enough time step to make the current non-singular, and a 'time step too small convergence fail' message will be issued."> Extra Hint!</b></font>
 *'''steady:&nbsp;''' Stop the simulation when steady state has been reached.
 *'''nodiscard:&nbsp;''' Don't delete the part of the transient simulation before steady state is reached.
@@ Line 38: / Line 38: @@
 === AC Analysis ===
-Perform a small signal AC Analysis linearized about the DC Operating Point.
+Perform a small signal AC Analysis (linearized about the DC Operating Point).
-The small signal (linear) ac portion of LTspice computes the ac complex node voltages as a function of frequency.&nbsp; First, the dc operating point of the circuit is found.&nbsp; Next, linearized small signal models for all of the nonlinear devices in the circuit are found for this operating point.&nbsp; Finally, using independent voltage and current sources as the driving signal, the resultant linearized circuit is solved in the frequency domain over the specified range of frequencies.
+This is a frequency domain analysis whereby the ac small signal (i.e., linear) response of the circuit is calculated using complex variable arithmetic.&nbsp; First, LTspice finds the dc operating point of the circuit.&nbsp; Next, working about this operating point, LTspice calculates linearized small signal models for all nonlinear devices.&nbsp; Finally, using independent small signal ac voltage and current sources as the driving signal, LTspice solves the resultant linearized circuit in the frequency domain over the specified range of frequencies.&nbsp; <font color="green"><b title="By specifying just a single frequency point and sweeping (stepping) any circuit parameter instead, LTspice will display the ac response over that parameter's sweep range."> Extra Hint!</b></font>
 This mode of analysis is useful for filters, networks, stability analyses, and noise considerations.

@@ Line 35: / Line 35: @@
 *'''startup:&nbsp;''' Solve the initial operating point with independent voltage and current sources turned off (but using any constraints specified by a .ic directive).&nbsp; Then start the transient analysis and linearly ramp on these sources during the first 20 us of the simulation.
 *'''step:&nbsp;''' Compute the step response of the circuit.
 === AC Analysis ===

@@ Line 25: / Line 25: @@
 Perform a transient analysis.&nbsp; This is the most direct simulation of a circuit.&nbsp; It basically computes what happens when the circuit is powered up. Test signals are often applied as independent sources.
-  Syntax: .TRAN <Tstep> <Tstop> [Tstart [dTmax]] [modifiers]
+  Syntax: .tran <Tstep> <Tstop> [Tstart [dTmax]] [modifiers]
-    or    .TRAN <Tstop> [modifiers]
+    or    .tran <Tstop> [modifiers]
 The first form is the traditional .tran SPICE command.&nbsp; Tstep is the plotting increment for the waveforms but is also used as an initial step-size guess.&nbsp; LTspice uses waveform compression, so this parameter is of little value and can be omitted or set to zero.&nbsp; Tstop is the duration of the simulation.&nbsp; Transient analyses always start at time equal to zero.&nbsp; However, if Tstart is specified, the waveform data between zero and Tstart is not saved.&nbsp; This is a means of managing the size of waveform files by allowing startup transients to be ignored.&nbsp; The final parameter dTmax, is the maximum time step to take while integrating the circuit equations.&nbsp; If Tstart or dTmax is specified, Tstep must be specified.
@@ Line 59: / Line 59: @@
 === DC Sweep ===
 === Noise ===
 === DC Transfer Function ===
 === DC Operating Point ===

@@ Line 16: / Line 16: @@
 {|table width="400" cellspacing="0" border="1" cellpadding="50" style="background-color: #DDDDDD" title="LTspice dialog box"
 |- align="center"
-| ''Various options for the active tab''
+| ''User options for the selected tab''
 |}
 __NOTOC__