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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59 views

How to increase output voltage of an op amp well above the supply voltage

I have a circuit which produces a (not high speed) signal between 0 and 9 volts with an adjustable slope, and I would like to increase this output voltage to between 0 and 200 volts, which keeping it ...
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1answer
361 views

Paralleled voltage sources error in LTspice

I have the following LTspice simulation schematic. (It's a simplified version, just to demonstrate my dificulty). The LTspice simulator returns a paralleled voltage sources error even when the ...
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How to flip LTspice voltage controlled switch so that it opens at threshold voltage? (versus close)

I am trying to figure out how to tell the VSWITCH of the LTspice program to open after it crosses the threshold voltage and close when it is below (with hysteresis). Normal behavior is that with Vt ...
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51 views

LTspice subcircuit with behavioral voltage source

I'd like to use behavioral voltage source in subcircuit block, as showed below: With block "comp": But when I try to simulate it doesn't work and gives mi this message: Someone could explain what's ...
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1answer
44 views

Getting following error in LTSpice simulation : “Too few nodes…”

I am doing simulation using LTspice and getting error as Too few nodes. I am using three external library components/parts. Could you please help me to identify where I am missing. Thank you. D1 -...
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65 views

How to reduce simulation time for large radio frequency signals (400 MHz) in LTSpice?

I am simulating circuit for input frequencies 10 kHz to 400 MHz, but its takes long time while simulating the circuit, so is their any alternative way to reduce simulation time and increase speed? ...
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34 views

Add LTspice IV library to LTspice XVII

I have an external library which works fine for LTspice IV. To add this external library, I simply overwrote (added) the corresponding files in the lib folder in the installation directory. Hence, I ...
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2answers
104 views

Why does the output of this opamp change my analog signal?

I am trying to make an inverting Op-amp circuit in LTSpice where I can invert an analog signal without any gain on my signal, I want the signal to stay the same but inverted. I have followed the basic ...
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1answer
51 views

LTspice Vs Matlab - Power electroncs

What are the advantages in power electronics of Matlab in comparison with LtSpice and vice versa ? Thank you very much and have a nice day ! :D
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Simulation LTSpice Miller plateau and reverse recovery diode

I would like to do a simulation in order to better understand the losses in switching power supply. I m trying to a simulation with the following circuits : I'm working at very high frequency in ...
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2answers
47 views

Why does LTspice resistor noise disappear when setting value with .param?

When performing a noise analysis in LTspice of a 1kΩ resistor, a noise level of 4nV/rtHz is simulated. However, if this resistor value is set to 1kΩ using .param, ...
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48 views

Total harmonic distortion vs frequency

Is there a way to plot the variation of THD of a circuit due to a frequency sweep of the input signal? I use LTSpice. Cheers
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1answer
46 views

LTSPICE P-Channel MOSFET

I'm learning LTSPICE and am very confused by the results coming from playing around with P-channel MOSFETs. I created a very complete test of P-channel and N-channel MOSFETs, and all the N-channel ...
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15 views

ltspice: assign list of values to .param

If I want to do a simulation for a set of .param values I can do .step param R1 1k 10k 1k. But this generates a set of ...
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24 views

Can't find definitions of model irfs4010

I'm trying to run on the LTSpice the circuit below. It's the circuit of a Boost-Converter. When I try to run, LTSpice shows the message "M1: Can't find definition of model irfs4010". Sorry if i'm not ...
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1answer
51 views

How to overcome current drop in circuit with high inductance value?

I have a very simple circuit that uses a switch to switch between a resistive loop and inductive + resistive loop. Whenever I switch from resistive load to inductive load, the current of the source ...
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1answer
47 views

THD analysis of an arbitrary expression in LTspice

Is it possible to perform .four THD analysis of an arbitrary expression in LTspice? It works seamlessly with simple expressions like ...
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56 views

LTspice .param variable component selection

Update: In case I could not explain myself clearly, I am reparaphrasing what I want to achieve. Let's say I will have 8 opAmps. Their symbol is opamp2 and their values will be LM741 with ".lib lm741....
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23 views

LTspice output of a bjt amplifier is offsetted

If I choose "start external DC supply voltages at 0" from transient simulation settings, the output is centered at 4.55 Volts. The amplification and gain is OK, but the output is not centered at 0. ...
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1answer
76 views

LTspice darlington model

TL;DR : I want to use a darlington transistor model(BD679&BD680) within LTspice. Can I do that by using default symbols npn or pnp from component selector menu? I have done it with TIP41C & ...
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104 views

Why does LTspice have a hard time to simulate this?

update : when the two-transistor structure is replaced by a darlington model provided as spice model by the manufacturer, the gain dependence of stable waveforms disappeared. Now, without those gain ...
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1answer
89 views

Why cannot I edit MOSFETs in LTspice by “nmos”

update: I edited question so that it will be mainly related to LTspice OK, now I have used irfz44n for an example model, I realized that, by using the directive above(nmos), I am not able to modify ...
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2answers
46 views

Lt-Spice doesn't give me all the information

Here is my LT-spice simulation of a simple circuit. I need to find the voltage across R6, but Lt-Spice doesn't give me that information. Does anybody know why this is or if there is something wrong?
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26 views

LTspice Sample Hold

I'm using the sample/hold blok in LTspice. As shown in the attached pictures and LTspice simulation, the output has not the same amplitude of the input. For example the input amplitude is 60kV while ...
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22 views

Can LTSpice used in command line on MacOS?

Can LTSpice used in the terminal by a command line? Is there any example there ? I only saw examples in Windows OS How would simulating a circuit file using LTSpice using terminal in MacOS? (like ...
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37 views

Buck Converter - Calculating Line and Load Regulation

I have a buck converter with a PWM circuit and Control Circuit in LTSpice. I'm wondering, how do I simulate values for load regulation and line regulation? I was thinking for line regulation I could ...
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34 views

Schmitt Triger Simulation in LTspice

I got a homework question as follows: I was able to create triangle wave but I am having problem with the output wave. It is not exactly a square wave. What am I doing wrong ? Simulate the ...
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1answer
58 views

Why does LTSpice simulation give me negative value on NPN emitter current?

So I built this circuit and I am trying to measure the emitter current, and the LTSpice simulation is giving me negative value reading... any idea why?
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20 views

Why do I get this LTspice Error message ‘Unknown VDMOS Level :3’?

I am new to LTspice and following this tutorial : http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_3.htm I am using the proposed Jig : LTC3878 buck converter that use 2 MOSFET, ...
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36 views

Sine wave clipping before rectifier when wire resistance is added at secondary of transformer in LTSpice

I'm simulating 4 different circuits, they are all power supplies, with loads, filter capacitors, rectifiers made by four 1N4007s, and transformers fed from 120VAC: They all have the same problem, ...
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1answer
52 views

Problem simulating current controlled current source in LTspice

I've been trying to simulate the following circuit in spice. (I'm plotting the voltage over R7) Everything is okay, and works as expected until I change the gain of the current controlled current ...
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33 views

Help with using a tunnel diode in LTspice

I want to use a tunnel diode to implement a simple van der pol oscillator circuit. So far I found a SPICE code for 1N4393 from this reference. Is it possible to simulate 1N4393 to convert and use ...
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3answers
76 views

LTspice, plotting a node voltage problem

Edit: The question is answered in a such way that I am happy now, however for the interested ones, the mystery of the question is still on. These two are the parts from my circuit, related to the ...
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3answers
386 views

CE amplifier non-sinusoidal signals

I am trying to learn some transistor amplification by simulating. However there is something I don't understand why. Why all waveforms are somehow distorted or bad-looking sinusoidal-ish waves ...
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1answer
56 views

LTspice a voltage source as a function of time

I saw the ability to control R by time in someone's drawing, tried it, and it worked fine. Then, I thought that I could use that "time" keyword also to control the voltage of a DC source. However it ...
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33 views

sallen-key bpf giving low gain after coupled to differential input

I designed a Sallen-key band pass filter where the gain at center frequency is 45.6dB. After feeding it with a sine wave at the center frequency, it amplifies the signal by 45.6dB. However, after ...
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2answers
44 views

What is the required VA rating of the transformer in this LTSpice power supply?

I have this circuit that I'm going to build, including the transformer. It is a simple power supply, with RC filters and one choke, I know all the voltages and currents. Because I will design, wind ...
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4answers
85 views

How to calculate RMS power of an offsetted sine wave

I know when it is centered at 0, Vpeak/sqrt(2) gives the RMS. When I do FFT on LTspice, it gives a peak at -17dB which is equal to 0.141254 On the FFT page, program says that it shows RMS values. ...
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21 views

how to pause/stop spice simulation in Altium Designer?

I am trying to simulate a circuit with Altium Designer. My simulation takes very long time, and I need to tweak the circuit frequently. Although I am able to stop/pause on-going simulation in LTSpice ...
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1answer
43 views

can not get required gain with gilbert cell on ltspice

I designed a very basic Gilbert cell using BJT's. The function is a DSB modulator where one input is a 2.5mvpp sine wave, and the other a 5vpp square wave. The current at the bottom is a simple ...
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2answers
26 views

Explanation results of RC simulation wih LTspice/Micro-cap

I built a basic schema with resistor, capacitor, ground and a battery in LTspice and MicroCap. I used transient analysis mode. I expected to see on a chart decreasing current and increasing voltage ...
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1answer
71 views

How to generate different noise in LTspice from run to run

I'm trying to simulate noise in my circuit, and ideally want to get a histogram of a certain parameter affected by that noise over many runs. However, when I use the white() command in LTspice, or ...
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2answers
94 views

LTspice transformer voltage course problems at low duty cycle

I am trying to simulate full bridge SMPS in LTspice where I can change the input voltage to the voltage regulator (LT317) by changing the pulse width of the PWM signal at the MOSFETs. Everything ...
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28 views

LTspice Transient Analysis Simulation error

I am simulating a boost converter, however LTspice is telling me the transient analysis is only 13.8 % done, as seen below. Why is this?
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1answer
38 views

LTSpice: why does my .MEAS 3dB calculation disagree with the cursors on the plot?

I'm exploring the .MEAS command with the following simple BJT Class-AB amplifier: And am getting the following results from my ...
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0answers
72 views

LT-Spice wont open file -> File limitations?

I am currently working on bulk simulations. For this I created a Python script which writes in the .asc files of LTspice and creates long tables, which are stepped through with the run variable. This ...
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23 views

How do determine MOSFET parameters in LTSPICE

I am designing a phase locked loop on LTspice (which I'm new to), but have come across a snag in the procedure: Is there a way to determine the output resistance of a mosfet (as the I'm not able to ...
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1answer
41 views

CD4006 Behavioral model in LTSpice

I want to simulate the behavioral model of CD4006 chip in LTspice. It is a CMOS 18-Stage Static Register. Looking at the Datasheet I see the one stage logic diagram that consist of inverting buffers ...
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1answer
93 views

LTspice not getting exactly -3dB point

Looking to answer another question on this site, to did some math and fired up LTspice to check some values and I am not able to the -3dB point. I found the transfer function to be $$ H(s) = \cfrac{...
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21 views

Easy-PC Circuit Simulator LTSpice Integration

I'm not a spice guru and i want to ask a question. When I start a design once draw on EASY-PC our official circuit drawing program, after draw one more time that same schematic also in spice. To avoid ...