# What is Ltspice: Definition and 54 Discussions

LTspice is a SPICE-based analog electronic circuit simulator computer software, produced by semiconductor manufacturer Analog Devices (originally by Linear Technology). It is the most widely distributed and used SPICE software in the industry. Though it is freeware, LTspice is not artificially restricted to limit its capabilities (no feature limits, no node limits, no component limits, no subcircuit limits).

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1. ### I don't understand why I'm getting this Thevenin resistance in my LTSpice circuit

Attached is an ltcpice net file. The thevenin resistance betweed the 3ohm and 6ohm resistor is 7.6 ohms. This works out as 3ohms plus the parallel value of 20||6 (4.6ohms). My problem is - Why is this the thevenin resistance, could someone please explain?
2. ### PWM sweep from 0 - 100% duty cycle in LTSpice

How do i simulate the PWM signal with duty from 0% to 100% in Ltspice. I can generate a pwm signal with single duty.
3. ### Mike Engelhardt, LTspice, and S·P·Q·R

Mike Engelhardt wrote and developed LTspice at Linear Technology over a period of 20 years. As the world's most widely used SPICE, it became a most valuable asset for Linear Technology. In March 2017, Analog Devices purchased Linear Technology for 14.8 billion dollars. Mike later left Analog...
4. ### Spikes in LTspice voltages and currents

Attached is a screenshot of an amp I am running in Ltspice. There are spikes on all the currents and voltages displayed, can anybody tell me why?
5. ### Common mode current simulation

Hello! I'm trying to model common mode current with LTSpice, but there is a problem with my simulation. Someone else tried on an other software and got the expected result, but I can't explain why. When going through the capacitor, square signals should become pulses, but that's not the case...
6. ### Analyzing a frequency-mixer circuit in LTSpice

Summary:: I'm trying to analyze a frequency-mixer circuit using LTSpice but i keep bumping into problems. Am I understanding something wrong? so I'm trying to design a frequency-mixer circuit. (the images are all shown below) in LTSpice, and there's a task asking me to perform a transient...
7. ### Engineering How can I find DC gain via AC simulation in LTspice

I use this netlist and simulation result came out as shown. I need to find the dc gain here and circuit diagram, but I'm not sure how. I would be very grateful if you could give me the answer.
8. ### LTSpice functionalities regarding its Frequency Domain Analysis

The time domain analysis is easier to plot compared to analyzing the frequency with respect to the phase. But, LTSpice makes it look really easy. So, for a small signal AC analysis, LTSpice does use a AC voltage source for its frequency domain analysis function. This must be a really convenient...
9. ### Help Plotting Phase Difference using LTSpice please

How do i plot phase difference in a Ltspice in this circuit ?
10. ### Gain limiter circuit in LTspice - current flowing in wrong direction

This is one more thread in my quest to learn simulations in LTspice. I am trying to simulate the gain limiter network shown in this video. A snapshot of the video is available for quick reference: My schematic in LTspice is shown below: For the simulation, I am using DC sweep on voltage...
11. ### What's wrong in my LTspice simulation of an Op-Amp integrator circuit?

I am doing an online course on op-amps. The specific video I am talking about is this one (skip to 24:25). Here, the professor has derived the expression of the op-amp integrator circuit, and in the next slide, he tells that we can create a triangular wave from a square wave using this...
12. ### Measuring ripple reduction in LTSpice

Dear friends, I am simulating a capacitance multiplier circuit and an RC filter circuit simultaneously. My aim is to check the reduction in ripples when using a cap multiplier circuit against an RC filter. I am familiar with ltspice but not quite an expert. I am comparing two output waveforms...
13. ### Could you check this Li-ion charging circuit?

Can secondary cell can be described in circuit simulator?? With other symbols like capacitor. Also I wonder if there's a program that provide secondary cell(like Li-ion battery). Please help me
14. ### Engineering Understanding the output waveform and using LTSpice

For the following circuit I need to find the output waveform. A. Conceptually I am at sea here but I will have a stab at it. My though process is as follows : At a given instant, the AC voltage is at a fixed value and this value drops (##V_drop##) across the resistor ##R##. The voltage...
15. ### Engineering Simulate a step-down chopper circuit using LTSpice

Simulate the circuit shown below sung LTspice.I tried to simulate it , but I didn't get the corrected result. Here's is my attempt: The result (voltage in the collector of the transistor) : Could someone let me know where is my mistake?
16. ### Line filter, proper LTspice simulation

Dear forumers, I have two high performance AC feedthrough capacitors (47nF, 100A, class Y2, DC-60Hz) which I want to either combine with a general purpose EMC line filter, or build a custom one to filter the mains from of about 100khz to as high as possible (for shielding purposes). I can see...
17. ### Unable to get the desired impedance in this LTspice simulation

Hello friends, I am studying an article on impedance matching which states about matching a resistance of 52 ohms with 2k ohm. It is accomplished by adding an inductance of XL= 318 ohms in series with the 52 ohm resistor yielding a parallel equivalent of 328ohm as reactance and 2k ohm as my...
18. ### Help with LTSPICE on a high frequency circuit

Hi, can you please tell me how would I be able to determine the effectiveness of a specific circuit, see in the attached spice file I tried to simulate a circuit , my secondary side is a self generating coil which in spice I had to simulate with mutual inductors aka a transformer, my basic idea...
19. ### RMS and DC Value Displays of Waveforms on LTspice

I hope I am posting this in correct forum section. I just downloaded LTspice for my Power Electronics course. Does anyone know if the software can display the DC component of a waveform such as found by determining the Fourier series of a waveform?
20. ### Nonlinear transformer model for simulation in LTSpice

I am looking for a comprehensive nonlinear transformer model, which should be available free, readily available for simulation in LTSpice and able to take account of various factors of nonlinear transformer including hysteresis characteristic, skin and proximity effect, leakage inductance...
21. ### Varactor (varicap) FV1043, equivalent in LTSPICE

Hello, everbody can somebody help me to find equivalent varicap diode of FV1043, i can't find in ltspice FV1043 is for oscillator to change the frequency….. thanks.
22. ### Current Through an Inductor at time t

Homework Statement Homework Equations [/B] V = 1/L di/dt I = Io x (1 - e^(-t/L/R) Tau = L/RThe Attempt at a Solution [/B] Ii = 0mA ; If = 1mA Vi = 1V ; Vf = 0V Tau = 15uH / 1k Ohms = 10ns If my above is correct, then voltage and current equations through inductor should be as follows...
23. ### Integral for Current through an Inductor -- Not Working

Homework Statement [/B] Calculate, and plot along with (on the same plot) the voltage seen below, the current flowing in the following circuit using the integral relationship between the voltage across an inductor and the current through the inductor. Verify your hand calculations and plot...
24. ### Engineering Design Circuit to Convert Current to Voltage | LTSpice Also

Hello, We just finished up midterms and I actually did well--got an A. However, somehow between the midterm (class before last) and last class we jumped to creating a circuit with a diode. I am pretty lost. 1. Homework Statement Homework Equations Voltage / Current = ResistanceThe Attempt...
25. ### Engineering Question About A Particular Circuit in LTSpice

I am simply attempting to design a circuit in LTSpice. We just started on dependent sources. I am having trouble designing this guy here: Here's what I've got: What does this error mean? What do I need to change to make this circuit work?
26. ### Help with building this transformer in ltspice

Hi, everything oko_O i just want to tell, can somebody, who have time just to read this file, you understand direct, if you know about fm detection, i just don't know how to make a transformer in ltspice, can somebody told how to make it this circuit with transformer and tuned please
27. ### Engineering Determine the input impedances of a circuit

Homework Statement I'm studying a circuit with BJT's and I'm asked to determine the input resistances of the two amplification steps of the circuit. The circuit I'm analyzing is the following one: Homework Equations 3. The Attempt at a Solution [/B] To determine the input resistances I...
28. ### 3N187, where to find this type of MOSFET in LTSpice

hello 3N187, where to find this type of mosfet in ltspice, , because i am reading one good book and i need this 3N187, any help is welcome
29. ### Generating TV spectrum in LTSpice XVII...?

Can some one tell me how to generate following signal on LTspice XVII.. Thanks..
30. ### How to model noise in LTspice

Hello, I try to add a voltage noise using an arbitrary voltage source set as V=white(1). Since I couldn't find any info about that parameter for the white() function I decided to do a .noise analysis to see how it responds to different values of that parameter. Except I can't get any kind of my...
31. ### Mis-matched pin count error in ltspice

Hi. I have a simple circuit with a third-part model. As far as I can tell using info from the internet I have everything correct, but I still get this problem. Please help me clear this log-jam, thanks!
32. ### How do you do a Bode plot comparison with LTSpice?

I'm trying to use LTSpice in order to fine tune LC circuits, but a road block I've hit is that when I run the simulation and generate a bode plot, the previous plot is overwritten, so I can't visually compare the effects of the L C changes. Some graphing programs have a function that let's you...
33. ### My LTSpice simulation is too slow

Hi, How can i make my Ltepsice simulation faster ? it is taking me too much time (three days and it is not complete) the Defi diodes are supposed to hold up to 4 kv
34. ### AC current / volatge with a mosfet in Ltspice

Hi, my Voltage Multiplier Simulation does not work properly the first transformer is working just fine, the second one does not really seems to work, for the second transformer i tried to creat AC current with a mosfet, but i think I am doing it wrong :/, can you give me some tips how to...
35. ### Transformers and Electric power Ltspice

Hi, i was looking for the Energy conversion efficiency of my circuit in Ltspice, but i find out that my Transformers is giving me strange power values i mean with K = 1 the P1 should be equel to P2 but in my case P2 is is way too small , i get equality 90% only if get rid of the Flyback...
36. ### Simple current limiter for LTSpice

Looking for a simple way to limit the current from a voltage source in LTSpice. Not a realistic or practical circuit, just something that will give me the behavior that I want. Hitting a total mental block with this, for some reason. What I want is for the source to act normally until the...
37. ### Drag the cursor to the the maximum amplitude using LTspice

Homework Statement So i am trying to find the maximum power transfer of a circuit. See attached image. Is there any way to automatically drag the cursor of a plot to the maximum/minimum amplitude of a signal when simulating LTspice? Or do you need to manually drag the cursor and estimate values...
38. ### LTSpice Clock signal distortion

Hi I made a counter using Dflop in Ltspice. But when I am using the count bits as signal to other circuits the clock signal is getting distorted. Why is this happening? How can I overcome this problem? Thanks Salil
39. ### LTSPICE or PSPICE, what is the best?

My teacher of circuit analysis showed us the LTSPICE but there are workshops on my faculty on PSPICE. What's the best software between this two or is there one better than this two?
40. ### Any frequency sweep feature in LTSpice?

Hi I want to find out is there any way to set up frequency sweep in LTSpice and plot the frequency response on a graph? I have look and I cannot find it. Thanks Alan
41. ### Calculate Delay of inverter in LTspice

Homework Statement I am trying to calculate the delay of the inverter. Homework Equations The Attempt at a Solution I tried to build the circuit in LTspice, but seems like I couldn't get anything useful from the plot. So I am hope somebody good in LTspice take a look with this and hope they...
42. ### Is there vacuum tube models for LTspice?

I know the default library of LTspice don't have vacuum tube model. Does anyone know where I can get one. If not, any other free spice program have vacuum tube models? The only one I find so far is: http://www.duncanamps.com/technical/ltspice.html I tried to follow the instruction and...
43. ### Strange impedance curve in LTSpice

Hi I'm looking at an impedance curve of a non-ideal tantalum capacitor in LTSpice. The test circuit and impedance curve is seen in this screengrab: http://www.apspektakel.com/bilder/tantal.png" The spice file is here http://www.apspektakel.com/bilder/tantal.asc". So, the imdpedance curve...
44. ### LTSpice: Adding an Ideal BJT NPN Transistor to Your Circuit - Tips and Tricks

I am just wondering, how do we add an ideal BJT npn transistor to an LT Spice circuit? From the component button i have added an 'npn1' will the default values be ideal? And what if you want to change the beta for the transistor how do you do this. I found a file called standard bjt, it...
45. ### LTC4440 LTSpice simulation problems?

Am I trying to use the LTC4440 as a high side mosfet driver, but when I run the demo simulation in LTSPice, this is what I get from the output from TG. There seems to be no boost to the gate control, so how can this drive any MOSFET, much less a FET with a drain voltage of 70 as specified on the...
46. ### Easily modifying BJT parameters in LTSpice?

I've created a multistage amplifier in LTSpice IV and want to use actual measured hfe (Beta) values for each of the transistors, though I can't find an easy way to modify them. I could modify their library values in notepad, but I am using the same transistor model for a few of the stages and...
47. ### Modeling I-V Characteristics in LTSpice

I'm trying to model the I-V characteristics of a few diodes in LTSpice. Though doing the DC sweep I have in the picture doesn't seem to give me what I want. I'm sweeping from -80V (It's breakdown is 75V) to 2V, in 1V increments. What kind of simulation do I have to run across the diode to get a...
48. ### Help with LTspice Measuring Input/Output Impedance

Does anyone know how to measure the input and output impedance of a bjt circuit on Ltspice? eg. a circuit like this
49. ### Engineering LTspice iv Laplace circuit design help

Homework Statement Find Io(t) for t>0 using Ltspice 4 Homework Equations n/a The Attempt at a Solution Here is what i have so far. I am unsure if i have the voltage source on the left correct or not. I am also stuck on how to use the current dependent current source from...
50. ### LTSpice IV simulation speed adjustments

Hi everybody. how r u. i'm using linear technology's LTSpice IV to simulate my dc/dc switching power supplies. for that I'm using the chips from the same company. the problem is that when i simulate the circuit using LTSpice IV the simulation speed that it shows is only 25microsecond/s which...