Questions tagged [ltspice]

Anything related to LTSpice. LTspice is a SPICE simulation, schematic capture and waveform viewer program from Linear Technology. LTspice is freeware with very liberal license, it is lightweight and isn't crippled in any way.

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DC DC converter simulation time slow in lt spice

Usually I can 'finagle' DC to DC converter simulations into working in a timely manner, this one has me stumped. I have done the standard gmin/abstol/reltol/cshunt combination, set initial conditions ...
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33 views

LTSpice: How to Add Trace of Two Swept Values

I'm sure there is a really simple explanation for this but I can't seem to figure it out. I am sweeping the series resistance of the source voltage and I am trying to see the transfer function output. ...
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264 views

LTSpice Sallen-Key Filter

I'm new to simulations on LTSpice with op amps (and LTSpice in general). I've been trying to simulate a Sallen-Key low pass filter and the simulation is nowhere near my calculations plotted with \$...
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265 views

string parameter in LTSpice

My question is whether is it possible to declare string parameters in LTSpice? My specific problem is that I would like to use PWL files for the simulation, and it would be very useful if I could give ...
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1answer
71 views

How to avoid the saturation of the current amplifier?

I have to calculate current gain of the following circuit and to model it in Spice. I arbitrarily set Is = 0.0002 A: Here are the results provided by LTSpice: Also, in order to find an equation for ...
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40 views

LTSpice -Resistor value controlled by on/off Switch

Is there a way to vary my resistor R4 in picture based on if the switch is on or off? For example, if S1 is off, I want my R4 value to be 10 Ohms, and if it's on, I want my R4 to be 100 OhmS. And if ...
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34 views

LTspice Monte Carlo with different model libraries

I'm trying to figure out how to do my first Monte Carlo analysis in LTspice. I have a very simple schematic that includes the SPICE model for PN 74LVC3G17DC (vendor link). The distribution from the ...
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4answers
8k views

How can I make an ideal comparator in LTspice?

For fast simulations I sometimes need an ideal comparator. I guess it is not a built-in component. How can it be implemented by ideal sources or VCVS ect.?
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79 views

Low-Speed CANbus Common-Mode Choke Insertion Loss

I'm designing a low-speed CAN transceiver breakout-board (schematic below) and I'm trying to select the proper choke to use to reduce common-mode noise. I've found a few common-mode chokes meant ...
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1answer
464 views

Two-tone alarm issues

I'm working on an inclass project, for a two-tone alarm circuit. The 3V source represents two AA batteries. We've implemented this successfully on a breadboard. The IC used for the Inverted Schmitt ...
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106 views

import touchstone file into ltspice [duplicate]

Does anyone know how to import Sparameter (touchstone) files into ltSpice and how to use them? I have downloaded s3p format file, but I don't know how to use it. I cant find any information in the ...
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2answers
90 views

Integral in mathematical expression of capacitor/resistor LTSpice

I know how to simulate a variable resistor in LTSpice. For example for a heating resistance the equation can be made by considering heating equation and can be expressed like R=(Ri-Ao*EXP(-time/To)) ...
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599 views

Why does LTspice XOR gate have more than two inputs?

LTspice has the following symbol for XOR gate: But as far as I can see the XOR gate has two inputs.
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309 views

S parameters LT SPICE

I read the help section on .net and found that i can use either a node (Vout) or a resistor (I(Rout)) to specify the output node. However the 2 give me different values of S parameters for the below ...
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122 views

Frequency comparator circuit in LTspice not outputting expected state

I'm trying to simulate the circuit in the method shown here in LTspice as: I use the same parts 74HCT74 and 74HCT00. But the circuit does not function. Here I set F2>F1 and the outputs at R1 and R2 ...
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2answers
188 views

How can I get FROM and TO times of trig on measure statement of LTSPICE?

I need to measure the voltage on two signals which have a difference of phase, so in order to do the measure that I need I have to get V1 (t) and V2 (t + delay_between_signals). One way to that is by ...
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1answer
101 views

LTspice DC-blocking capacitor not working

I have been busy with a frequency shift keying modulation circuit in LTspice. The modulator works but I have this horrible DC-offset! I have tried high-pass filters and DC-blocking capacitors but I ...
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6answers
8k views

How do I update LTspice IV for macOS?

On an iMac and a Macbook, both running macOS Sierra 10.12.6, I have installed the latest LTspice IV (Build Oct 3 2016, 14:49:11 US Pacific), which prompts me to update on launch. Attempting to do so ...
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135 views

SCR triggering in LT Spice

I have been trying to trigger a SCR in my circuits but an error shows up every time. Unknown subcircuit called in xu1 n002 n001 n003 scr This is a screenshot of ...
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1answer
71 views

DC-DC converter not simulating correctly

I am trying to design a solar charge controller to charge a 12V battery, my solar panel is made of 9 cells that are 5W and 0.5V per-cell. I would like to make a booster circuit to get the voltage up ...
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1answer
169 views

How to assign the same value to multiple resistors in an LTSPICE circuit

I have around 10 resistors in a circuit, all with the default value "R". I defined the directive .param R=100 Upon running the simulation, I get the error ...
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154 views

Error converting PSPICE model for LT Spice

I'm using LTspice XVII, and I'm having issues generating components from PSPICE component files. Previously, I was able to follow the method of opening the netlist file, highlighting the name, right ...
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3answers
96 views

Failed to plot junction capacitance versus reverse voltage in LTspice

The 1N4001 diode's junction capacitance versus reverse voltage plot is given as follows: I guess to measure this capacitance they applied 1MHz 50mV pk-pk sine wave signal as reverse biased and varied ...
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3answers
619 views

Multiple output noise analysis with LT spice

If I want to do a noise analysis I do this in LT spice: .noise V(adc1) V6 dec 12 0.01 1e9 Where V(adc1) is the voltage for the output node of the analysis and V6 ...
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1answer
118 views

LT spice not predicting instability

I'm trying to make a linear regulator using an op amp and a pass transistor. Here is the circuit: From my limited understanding you can predict the stability of the circuit's feedback loop by ...
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1answer
1k views

How do I import a spice model into LT spice?

I decided to create a question of how to import models into LT spice since there were questions that are related but no definitive guide on how to import 3rd party models on this site. There are many ...
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28 views

LTspice Monte Carlo analysis vs. .meas command

I designed some analog second-order all-pass filter in LTspice and provided Monte Carlo analysis as well. I want to evaluate the obtained AC results with .meas command, particularly: Magnitude ...
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4answers
79 views

LTspice - analyze current with varying resistance

I would like to graph current from V1 over varying resistance instead of voltage. Is there a way to do this?
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1answer
227 views

LTspice: time step too small error

I am unable to run ltspice simulation. I have tried changing the solver to alternate, adjusting Gmin and Trtol, Changing integration method. Always get the same error. Error message: Analysis: time ...
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1answer
47 views

Is this way of plotting AC current gain in LTspice correct?

I want to plot the AC current gain versus the collector current in common base configuration. Ac current gain "alpha ac" for CB configuration is defined as the change occurring in collector current IC ...
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1answer
58 views

LTSpice error with the V() function in a subcircuit

I'm trying to do a simulation with a subcircuit, and I've narrowed down the issue to the V() function. The simulation fails with the message 'can't find definition of model "V" ' Here is the spice ...
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1answer
84 views

Output characteristics curves do not merge in LTspice

I wanted to plot the output characteristics curves and Early effect of a transistor in CB arrangement. In LTspice I made a DC sweep along with parametric sweep as follows where I sweep the Vcb from -...
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2answers
452 views

LTspice XVII solving Thevenin Resistance basics

Thevenin voltage is a snap, but how do I get R Thevenin?
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3answers
136 views

Weird LTspice XVIII behaviour

I was designing a circuit, when I noticed some unexpected behaviour regarding \$V_{GS}\$ of the PMOS in LTspice XVIII. I have reduced the circuit in order to point out where the problem lies. D3 was ...
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1answer
350 views

Symmetrical components

I am trying to build an abc to positive/negative/zero components transformation block (in LTspice), I did it, but sometimes I get erroneous behaviour: DC levels seem to be "omitted" at the output for ...
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3answers
11k views

Is there a portable alternative to LTspice? [closed]

I am constantly on the move and come across many computers to which I have access and which have some version of Windows installed. I was wondering if there's a portable alternative to LTspice (or if ...
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1answer
62 views

Output Voltage Formula verification of Operational Amplifier circuit

I'm trying to built an op-amp circuit for a PT100 temperature sensor. I've found the following circuit diagram online (from a polish website): And I'm trying to find the formula for the output ...
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1answer
253 views

LTSpice “Unknown parameter ”\“”

I am trying to simulate an electrical model (Mason Model) of piezoelectric system in LTSpice. So, I use parameters and formulas to evaluate the value of the passive elements in my circuit. I use the ...
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2answers
200 views

BJT astable multivibrator generate triangle wave

In this circuit there is a bjt astable multivibrator. It generates a square wave. And according to the description, at the output of the opamp it generates a triangle wave from this square wave. I've ...
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3answers
859 views

LT Spice Voltage Output

I am using LT Spice for simulation of my circuit. I have used a probe to check for the voltage on the Capacitor. What is the green dotted line that can be seen in the plot? Thank you.
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230 views

I am not able to edit existing LTspice directives; I always need to create new

Once I place the directive command I will not be able to edit it -Rarely I will be-. So I always make a new directive when I need to edit the already existing ones. I have re-installed LTspice, with ...
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1answer
74 views

Why I can't get the desired output when simulating this dc to dc converter circuit?

I found the below attached circuit of the TPS54560 4.5V to 60 V input, 5 A step-down converter. It is supposed to give an output of 10.8 V but when I simulate it I can't get more than 1.5V or 2V. I'...
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1answer
3k views

Error on importing 3rd party model into LTSpice

I'm new to LTSpice but have the basics figured out (laying out a schematic, setting up simulation, running) and have done so with the basic but very well stocked library included. Of course my issue ...
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33 views

Constant current limit in the SIMPLIS

I wanted to convert this error amplifier form Pspice to SIMPLIS, for now i am using voltage controlled current source (VSCS) with the FB nod to the negative and Vref to the positive node of the device ...
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1answer
139 views

Simulation on LTSpice

LTSpice does not have a gap sensor as a component. Is there anyway I can either download a gap sensor or is there a way to create my own one.
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38 views

2:4 Decoder on LTSpice [duplicate]

LTSpice does not have a decoder component so I have had to make my own using two inverters and four AND gates. I am not sure if I have done it correctly.
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2k views

3-Phase Inverter simulation

I'm trying to simulate a 3-phase inverter for BLDC(PMSM) in LTSpice. The problem is that drain current is way too high and also phase voltage isn't right. **New image *One leg If I put one source(...
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12 views

Simulation of decoders on LTSpice [duplicate]

I need to simulate a 2:4 decoder on LTSpice however the component does not exist. Does anyone know of a way to simulate it?
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1answer
60 views

MOSFET output voltage vs. gate voltage

I don't understand why I am getting this behavior from my MOSFET circuit. Either because I'm not using LTSpice correctly, or I'm not understanding MOSFETs. I set up the voltage to the gate to be a ...
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1answer
139 views

Some LTspice questions. Decoupling capacitor doesn't effectively block DC. Pull up resistor voltage doesn't drop to logic low level

I'm trying to design an interfacing board that is used between a micro-controller and a phone simulator (a picture of the schematics is attached). The 44VDC is used for the phone simulator to detect ...