Analysis

LTspice-Independent Voltage Source Setting

LTspice requires setting of the signal source when simulating.

In this article, we will focus on how to set up a independent voltage source for analysis.

For the types of analysis, please see the following article.

How to open “Independent Voltage Source”

Signal source settings can be made on the “Independent Voltage Source” screen.

1

Click “Component” from the toolbar of the schematic editor screen.

2

Select “Misc” and click “OK” or double-click “Misc”.

3

Select “signal” and click “OK” or double-click “signal”.

4

After placing “signal” on the schematic, “right click” of the mouse to open the editing screen.

5

The “Independent Voltage Source” screen opens and you can set the signal source.

Cell and voltage can also be used as a source

Component models of “cell” and “voltage” can also be used as signal sources. However, I think that it is better to use the part model of “signal” as a signal source as it is indistinguishable from the usual power supply.

If you want to set the signal source in “cell” and “voltage”, right click of the mouse on the part of the schematic, and the screen of the above image will appear. Click “Advanced”.

Then, the “Independent Voltage Source” screen opens, and you can set the signal source.

Independent current source settings

Although this article describes how to set up a “Independent voltage source”, you can set up a “Independent current source” as well.

Common settings

In “Independent Voltage Source”, “DC Value”, “Small signal AC analysis (. AC)” and “Parasitic Properties” can be set in “Common Settings”.

DC Value

Setting Explanation
DC value DC voltage value


※This can be set only when “none” is selected in “Function”.

Small signal AC analysis(.AC)

Setting Explanation
AC Amplitude Amplitude of AD waveform
AC Phase Phase of AC waveform


※Set when simulating AC analysis (.ac).

Parasitic Properties

Setting Explanation
Series Resistance[Ω] Series resistance value
Parallel Capacitance[F] Parallel capacity value

Functions

none(DC signal)

Setting Explanation
DC value DC voltage value

PULSE

Setting Explanation
Vinitial[V] LOW level voltage value
Von[V] HIGH level voltage value
Tdelay[s] Delay time from 0 to operation start
Trise[s] Rise time from LOW to HIGH
Tfall[s] Fall time from HIGH to LOW
Ton[s] HIGH level time
Tperiod[s] One cycle time
Ncycles Repeat count
(Continuous output if not input)

SINE

Setting Explanation
DC offset[V] Offset voltage value
Amplitude[V] Amplitude voltage value
Freq[Hz] Oscillation frequency
Tdelay[s] Delay time from 0 to operation start
Theta[1/s] Damping coefficient
Phi[deg] Phase difference
Ncycles Repeat count
(Continuous output if not input)

EXP(Exponential pulse wave)

Setting Explanation
Vinitial[V] LOW level voltage value
Vpulsed[V] Maximum value of HIGH level
Rise Delay[V] Delay time until waveform rises
Rise Tau[s] Rise time constant of waveform
Fall Delay[s] Delay time until the waveform falls
Fall Tau[s] Fall time constant of waveform

SFFM(FM wave)

Setting Explanation
DC offset[V] Carrier offset voltage value
Amplitude[V] Amplitude of SINE carrier waveform
Carrier Freq[Hz] Carrier frequency
Modulation Index Modulation Index
Signal Freq[Hz] Signal frequency

PWL(Piece Wise Liner wave)

Setting Explanation
time[s] n time
value[V] Voltage value at n time

PWL FILE(PWL wave file input)

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