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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39 views

LTspice - Flyback simulation misunderstanding

I am trying to understand how to compute the rms current through the output diode of a flyback with multiple outputs. To make it simpler, I did not add the leakage inductance of each windings. Here is ...
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RC circuit - phase current

I have a simple RC circuit as below : I'm trying to visualize current curve and voltage curve (Vout and I(R1)) vs Vin using LtSpice and I obtain the result below: It's OK that the Vout is leading ...
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LTspice - Measuring the resonant frequency

I would like to measure the resonant frequency automatically in LTspice, i.e. with the command ".meas" of the following waveform. Is it possible to do it by using the FFT plot? I have tried ...
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Increase the size of ltspice error log file contents

In my circuit when I am sweeping many values and total combinations are higher (>2K), only initial values are captured when using .measure command for each combination. I want to increase the ...
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42 views

How does a multi-meter diode check work and how to test an RF diode with it?

This is a followup question for Can I debug this simple circuit without VNA and proper RF equipment? which I am still fighting. The diode as a nonlinear element could explain all the weird behavior I ...
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Beginner's LTSpice Question: Why does my sine wave look so bad and how can I fix it?

I'm planning on building a Spice circuit with variable-gap capacitors. The capacitance in general will be something like C = eps*A/(g0+g'), where g' is the oscillation that occurs on top of the ...
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39 views

LTspice simulation problem when changing the load

I have this simulation. I tried to do a simulation for observing cross regulation problem: Here are the results: The two outputs are equal and stable which is normal. Nevertheless when I change the ...
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61 views

Non linear behaviour of a pure LC: Is it real or LT Spice is broken?

Questions: 1) Is the observed behaviour correct? (both cases at the resonant frequency and at a lower frequency) If it's not correct, why LT Spice is giving this result? 2) Why does circuit lab give a ...
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Hartley Oscillator Simulation

Hello i want to simulate the following Hartley Oscillator that i designed on LTspice But when i run it i am not getting the sine output. Where is the issue? How can i get a correct output? UPDATE ...
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40 views

Does spice model saturation recovery of bipolar transistors?

When a bipolar transistor is driven into saturation, it builds up charge which slows the recovery time when it is switched off. What I would like to know is, how well is this behaviour captured in ...
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Simulate and Plot each Vout given 40 Resistances and a 4 Resistor Network

I have a list of 40 different resistances and a 4 resistor network with which to substitute these values into. I want to be able generate values of Vout(Vadc) given every permutation of 40 different ...
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What is the “DanTherm” model in the SOATherm library in LTSpice?

LTSpice's SOATherm symbol has a "user-defined" option in the models list but I can't find any documentation on how to use it. Out of curiosity I opened the .lib file and there is a user-...
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Appending plots in LTspice

The single most important thing I miss in LTspice is the ability to plot things of multiple runs on top of each other. Cadence Virtuoso calls that "Append Plot". What I mean: I want to plot ...
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simulating gain vs parameter in LTSpice

I tried to dc sweep V3 in my circuit and measure the gain. But it does not give a correct result. What I am trying to do is actually recreating some measurements from the datasheet. Maybe there is a ...
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35 views

Ltspice - Simulation problem of cross regulation in a multiple output flyback

I am trying to show the effect of the leakage inductance on a multiple output flyback. According to those documents from Unitrode and texas instrument (this one : https://www.ti.com/lit/ml/slup081/...
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LTspice three phase rectifier simulation

I am interested in creating from scratch a regulator rectifier for motorcycle. I struggle to comprehend the ground placement in the simulator. I cannot find instructions about tree phase simulation. ...
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32 views

Digital gate in LTspice not all availabe and no generic NOR gate?

I tried to find a NOR gate in LTspice but seems there is only Or gate with multiple inputs. I tried also to import a third party but could not find a generic NOR gate
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67 views

Accuracy when measuring THD with LT Spice for AB Audio Amp

I've designed and built my own AB class audio amplifier circuit. I designed it to have as low THD as possible, using LT Spice to run my simulations with the .four command, so I created a bunch of ...
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48 views

LC Oscillator Simulation

I am designing a LC CMOS Tail injection based Oscillator but somehow the node voltages are constantly showing errors. The circuit schematics are The properties of MOSFETs are as followed: Node ...
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Why my circuit simulation is overly slow? Is there a way to solve this problem?

I'm doing a project in a working for my a subject in my university. It is a remote controller, and I know much probably there's a better way to do it, but I only can use this component: voltage switch,...
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60 views

SMPS stability near and above switching frequency

I am simulating in LTSpice a switched-mode power supply (LT3845) at a frequency of 150kHz. I am measuring the loop gain at the feedback node according to this article. The way I understand it, the ...
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54 views

Using TI Model in LTSpice

I'd like to use a TI model for the SN74LVC1G17 in LTSpice. https://www.ti.com/product/SN74LVC1G17#design-development##design-tools-simulation I've tried importing the .lib file into lib/sub and using ...
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58 views

Output of sawtooth generator circuit always 0V in LTSpice

I am trying to simulate a basic sawtooth generating circuit using an opamp integrator and a Schmitt trigger. However, for some reason, all the output voltages in the following circuit are always 0V: ...
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40 views

LTSpice - Opamp Buffer Input Impedance Measurement

I tried measuring the input impedance of Opamp LT1128 Buffer using LTSpice. And from the simulation then maximum impedance is showing only 20k. This particular opamp has 300MEG common mode input ...
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IR incandescent lamp modeling in ltspice

This is my first post here, I’m new to electronics and am trying to model the IR source to make a suitable driver circuit for it. so, how to build a ltspice model to match the specifications shown in ...
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1answer
75 views

LTspice simulation, timestep too small error

I already received a few tips from user 'a concerned citizen', but decided to start a separate question. This is the schematic: This simulation takes about 1:10 to complete the first 8.6 ms on a ...
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33 views

LTspice IR2110 Nmosfet error simulation

I got a task of building pure sine wave inverter, and I wanted to simulate my circuit before building it. File is in link. Problem is that the simulation stops after few seconds with error message: I ...
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48 views

What am I doing wrong when I try to set a switch voltage on LTSpice?

I was trying to set a switch voltage, I follow in according every tutorial that I've saw on the internet. However, I'm getting the warning saying : "Cant find the the model of SW." But it ...
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44 views

Need help finding a specific node in my schematic

I'm getting a Time step too small error in LTspice. It says it's having trouble with node "e:u2:_e27#branch". I assume ...
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45 views

how LTspice integrates Laplace in the time domain?

I modeled two different PID controllers with Laplace and with the same control parameters in LTspice, but the results show me the same behavior of the two PID controllers in ...
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how to simulate a Laplace function of a PID controller in the time domain with LTspice

I tried to simulate a Laplace function of a PID controller with LTspice in the time domain, but an error message appears "The laplacian is singular at DC". cs1 is the controller, so I just ...
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38 views

AM circuit LTspice

I have to analyze the following circuit and understand its function. As far as I understand the top part is the simple phase-shift oscillator generating output sine wave at circa 145kHz. The NE555 is ...
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34 views

Library file error while using a Third party component( INA138)

I want to use the INA138 as a current sensing amplifier but its symbol is not available in Ltspice so I downloaded the .lib File from https://www.ti.com/lit/zip/sbom140 here. I then opened the file in ...
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56 views

Using a behavioral voltage source as a zero crossing detector for inductance current in LTSpice

I'm trying to simulate a buck converter IC in LTSpice (MP4569) based on the functional block diagram from the datasheet using behavioral voltage sources to represent the logic from the block diagram. ...
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58 views

OpAmp Spice Model: Offset vs Common Mode Voltage

The spice Model of the OPA350 specifies that the DC Offset Voltage vs Input Common Mode voltage is implemented in the model. If I do the simulation however, all I can see is a linear trace, when x ...
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1answer
98 views

Having trouble properly driving a MOSFET

I'm trying to build a pure sine wave inverter in LTspice (Image 1) but I'm running into some trouble. So far, it consists of three main parts: The SPWM generator generates an SPWM signal from a 200kHz ...
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117 views

LTspice error “could not open Library file” when trying to use TL431 model from TI

I downloaded the LTspice model of TL431 from the Texas Instruments website, but I am not able to simulate the circuit given below due to this error: "could not open Library file" https://www....
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56 views

Non ideal inductor equivalent circuit

I'm simulating a non-ideal inductor. For this, I use the equivalent circuit implemented on LTspice which models the parasitic components (Rp, Cp and Rs). I tried to calculate from the data sheet the ...
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2answers
76 views

Real relay in LTSpice?

Does anybody know if it is possible to create a true relay in LTspice, one that is a true open circuit when open? The problem I am having is no matter how big I make the off resistance, there is ...
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1answer
94 views

How to properly model an linear power supply with LDO in LTspice?

I've build the following linear power supply: Before building it I tried to model it in LTspice. I couldn't find an LTspice model of L4941BV LDO (datasheet [PDF]) or a suitable replacement. Thus I ...
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33 views

AC divider circuit used to charge a capacitor

The following circuit uses a capacitive divider network along with a diode rectifier to charge a capacitor. I assumed that once C2 is charged to its maximum( calculated to be around 14mV) the diode ...
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Question about common mode input range

With this drawing I want to simulate the behavior of the following differential amplifier. I only draw half of the differential amplifier. Because I think they are equivalent. But when I simulate it, ...
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73 views

LTSpice AC Simulation giving unexpected output

I am currently working through AoE, 3rd Ed., and am on Exercise 3.7 (pg. 180). I am trying to find the -3dB point of the circuit pictured, and I am using LTSpice to check my answer. LTSpice says the -...
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44 views

MOSFET in LTspice sim conducts below the threshold voltage

Electronics noob here! I'm trying to create a circuit that feeds the output of a piezo transducer into a comparator, in order bring an arduino pin high when the piezo's output exceeds the comparator's ...
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1answer
37 views

Crude LTSpice gate driver model of buck converter

In the datasheet above LM3743. I have developed crude gate driver. To verify the circuit i have connected filter circuit and given expected duty cycle for Vout =1.8V Vin= 3V. Boost capacitor and ...
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1answer
59 views

LTSpice provides incorrect bode plot

I want to replicate this structure in LTspice where the components 1, 3 et 4 are resistors with the same resistance R and 2 et 5 are two capacitors and opamp LT1356 this is the schema I made this ...
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93 views

LTSPICE problem while trying to run third-party model

I have an error while trying to run a third-party model in LTspice XVII and I am not sure what this means M1: Only a level 9 B3SOI can have 5 nodes I am running it ...
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Basic Series RLC circuit with LTspice

The L and C have the same impedance at 14.529kHz. The series LC is at resonant frequency and should act as a short. Therefore R2 should have the same current as R1. However it is nowhere close. When I ...
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23 views

Information on LTSpice switching regulator macromodels?

I have read this Design Note 12 from Linear Technologies titled “An Op Amp SPICE Macromodel”. I was wondering if there is similar technical information about the macromodels of switching regulators (...
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37 views

Overlay waveform in LTSpice

Overlay AC plots using text file I tried using PWL source and attaching transient simulation text file from other LTSpice schematic run this works good. But when I try AC simulation this is the error....

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