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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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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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19 views

import touchstone file into ltspice

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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1answer
20 views

How to install a scr model in ltspice

I have downloaded an scr model file from this website and pasted it in the same folder as that of my .asc file. But ltspice still shows unknown subcircuit called for the scr present. What am I doing ...
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1answer
52 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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30 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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46 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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1answer
41 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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2answers
69 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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24 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
54 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
48 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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71 views

Why is the cutoff frequency of this highpass filter with formula different from LTspice?

I used this online tool to play around and design a Sallen-Key low pass filter with a cutoff frequency of 0.3Hz. When I now put the resulting values for R1, R2, C1 and C2 in the formula I get exactly ...
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3answers
57 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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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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48 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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4answers
61 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
49 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
40 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
40 views

LTSpice error with V() function, … when referencing net within a subckt (V(subCktName.NetName))

I've converted an IBIS model to a SPICE model using microCap, and am trying to simulate that subckt with LTSpice. Using LTspice, I get an error with the subckt in the library. "u1:g1: Unknown ...
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1answer
41 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
66 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
38 views

LTspice XVII solving Thevenin Resistance basics

Thevenin voltage is a snap, but how do I get R Thevenin?
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3answers
72 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
46 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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2answers
94 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
111 views

LC Circuit LTSpice Simulation

I'm sorry if this topic isn't adequate for the forum. Does anyone know how can I make this LC circuit simulation for \$v_{c}(t)\$? The original circuit is the one shown in the figure. \$v_{C}(t)=\...
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2answers
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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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3answers
824 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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1answer
61 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
83 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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1answer
54 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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0answers
22 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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3answers
98 views

Sine Wave Input for Op Amp Integrator but Output Looks Weird

The input is in sine form (AC input) but the output (in blue color) is the straight line. So what is wrong with my schematic in LT Spice this time? I thought I should've got output in sine form if I ...
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1answer
80 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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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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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
46 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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2answers
56 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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1answer
72 views

How can I export the frequency response from LTSPICE without phase wrapping?

After I plotted the frequency response of a circuit using LTSpice as shown: I exported the plots data as a .txt file in order to plot them after that using MATLAB, however, after I plotted the data ...
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1answer
41 views

LTspice stacks data points on the same vector when I do linear parameter sweep

I am trying to export the voltage of a transformer for different mutual coupling values. However, when I do a linear increase of mutual coupling it seems that LTspice will stack the parameters in one ...
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2answers
76 views

Wrong frequency response - LTSpice

So I have this simple OP-AMP circuit that is supposed to be a low-pass filter for which I made the calculations so it passes all frequencies below 1591 Hz (approx). The values of the components are in ...
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2answers
57 views

Ideal LC circuit decays over time in LTspice

I was trying to simulate a transformer without a load, and setting an initial condition to observe how the energy will flow from the primary to the secondary circuit. I realized that the energy will ...
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73 views

opamp constant-gm bias circuit

I try to incorporate the constant-gm bias circuit (Figure 6 in Improvements_in_biasing_and_compensation_of_CMOS_opamp) into the PFC (positive feedback frequency compensation) opamp, but it resulted in ...
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3answers
96 views

LTSpice: Produce Bode Plot for Compensated & Uncompensated Boost Converter

I am designing a product which uses the LTC3122 as a 5V-12V boost converter (datasheet here). This particular device provides the ability to add gain compensation, phase lead, or both. In my case I am ...
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1answer
67 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 ...
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44 views

Estimate Phase Margin in Spice

I am trying to determine the phase margin of my design and I have come across two methods for modeling the open loop gain in spice. The problem is they are yielding slightly different results. I have ...
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1answer
52 views

Sinusoidal voltage source not being sinusoidal in LTSpice

I'm trying to obtain the output resistance (resistance from collector node) of the following circuit By inspection, it should be the output resistance of a common emitter amplifier with degeneration ...
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54 views

opamp simulation

Is the following open loop transient simulation of opamp correct ?
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2answers
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LTspice : using a sqrt(-1) in behavioral model

i would like to simulate an equal circuit of two coupled inductors, So i need a behavioral voltage with following expressions: V=jwI(R2) LT spice do not recognize sqrt(-1), any idea for simulating ...
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68 views

Magnet Shake Generator - how to replicate in LTspice?

I made a generator for my wife's 3rd grade class, since they are learning about magnets, electromagnets and electricity. It's a simple pipe with a stack of magnets inside and you shake it to produce ...