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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14 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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81 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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406 views

Lt-spice switch model

I have a very simple circuit and want to see the current in the inductor. But I do not know why switch is behaving like that... Actually, I supposed to get KA range current. but it gives me very ...
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39 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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102 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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2answers
192 views

\$pV/\sqrt {Hz}\$ in Power Spectral Density

I am trying to plot a Noise Spectral Density from 10 kHz to 1 MHz. The Graph shows a cure which at 1 MHz the noise is 76 pV/rootHz. I am unable to understand that unit definition here. Becuase the ...
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23 views

H-Bridge Simulation for pure inductive and capacitive loads

I am trying to simulate full bridge inverter for pure inductive and capacitive loads. However the waveforms are not what I expect. I already simulated with a resistive load where both voltage and ...
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1answer
757 views

Import MCP602 Model into LTSpice - Timestep Error

Good evening Community, I would like to use the MCP602 model in LTSPice, but I am having simulation errors. Please see schematic below. I have downloaded the model from Mircochip and opened it via ...
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1answer
338 views

Frequency dependent capacitor for AC sweep analysis in LTspice

I need to model a frequency dependent capacitor for AC sweep analysis in LTpsice. I see that it is possible for inductors with GLAPLACE component, but I don't find anything about capacitors. The value ...
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2answers
44 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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23 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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1answer
2k views

A question about a circuit simulation using LM331 in LTspice

I'm trying to convert 0..10V analog voltage to frequency by using an LM331. Since LM331 works at 5V supply, I can scale 0..10V to 0..5V and feed it as the voltage input to the LM331. I came across ...
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18 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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32 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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31 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
54 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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1answer
424 views

ltspice, unrecognized option rshunt

I'm using LTSPice XVII. I'm trying to set a resistor to every node, helping convergence. This is not recognized (spell?) .options rshunt = 1e12 however, ...
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16k views

LTSpice's ltline (lossy transmission line) symbol slowing down the simulation process. What can I do?

LTSpice has the element called Lossy transmission line (symbol name ltline): I tried to simalate a pretty simple schematic: R2,...
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1answer
224 views

Test cases for for OTA in LTSpice

Here is a component OTA provided by LTSpice which has inverting non inverting common and output node. I am in process of modelling this OTA behavior form LTSpice to PSpice. I reffered this link for ...
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1answer
123 views

3KW SR motor gate driver and simulation questions

I'm designing power electronics for 3-phase 3KW SR motor by using power MOSFETS of rating 600V. To drive the gates of these MOSFETS, I'm using IR2183 gate drivers, one per each phase. The DC voltage ...
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3answers
71 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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15 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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34 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
49 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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32 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
362 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
49 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
43 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
75 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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17 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
109 views

Wheatstone bridge and difference op-amp

I use Wheatstone bridge as a dual voltage divider to feed both inverting and non-inverting inputs of differential op-amp: Theoretically voltage can be calculated using voltage divider expression: Va =...
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2answers
82 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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60 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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1answer
412 views

Simulating varicap diode in LTSpice

I have been looking into making a voltage controlled oscillator using varicap diodes, however I have had hard time simulating the diodes in spice. Would anyone here have an idea how this would be ...
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1answer
90 views

SiC MOSFET SPICE model not behaving properly

I have been trying to simulate a fully controlled full bridge using SiC MOSFETs and so far haven't gettng at least expected results. So I tried to check what is happening using a single MOSFET and a ...
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1answer
41 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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1answer
421 views

Simulating ADL5536 Gain Block with Ideal Amplifier

I'm trying to simulate the ADL5536 Gain Block in LTspice. A link to the datasheet can be shown below: http://www.analog.com/media/en/technical-documentation/data-sheets/ADL5536.pdf Analog Devices ...
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0answers
159 views

How to interpret LTspice simulation outputs for improving dual channel boost converter design using LTC3788

I am working on a boost converter design using the LTC3788. I would like to take advantage of the dual output capabilities of this chip to produce 24 VDC at 4 amps on one output and 48 VDC at 2 amps ...
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2answers
24 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
98 views

Long-tailed pair - gain and bandwidth

I'm trying to understand this schematic of this differential probe: I marked some blocks. I have some questions about the block I marked "Long-tailed pair" (LTP). I have no experience with LTPs so ...
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1answer
62 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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27 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
22k views

Help Converting a PSPICE MOSFET .LIB to an LTSPICE .SUB

I am designing a buck-boost regulator for a course at school and I would like to use the OnSemi ntk3139p PMOS transistor. OnSemi provides a few spice models for this part and I am getting stuck ...
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1answer
36 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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1answer
39 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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22 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
88 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 ...
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1answer
30 views

NOT valid mode type SIMetrix from Netlist

I am trying to run PSpice netlist in SIMetrix .cir and it says NOT valid mode type SIMetrix from Netlist, do we have to add any command other than this.