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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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Specifying channel length of NMOS

What is the syntax to specify channel length of a nmos in LT Spice ?
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1answer
45 views

BJT LT spice DC transfer characteristic

Why is it that the DC transfer characteristic isn't flattening out at -5 v, so it looks like a Z-shape? I did a DC sweep from -10 V to +10 V. The input wave is a 2V sine wave for the graph below:
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Modelling 3-phase induction motor and filter for inverter output in LTspice

I am designing an inverter in Ltspice and am looking to have a simple circuit to represent the motor load and filter out the PWM harmonics in order to obtain outputs. The motor characteristics are: ...
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1answer
58 views

Need help with three-stage transistor amplifier in LTSpice

I am currently attempting to design an amplifier in LTSpice for an E1 project. My professor tends to emphasize analysis of these circuits, so he hasn't really given us any kind of a design process to ...
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1answer
43 views

How to do a transient simulation using LTspice? [on hold]

I have the following circut that resembles a CMOS inverter. Now I want to do a transient simulation on this circut but I am not sure how to do it. I always get a straight line! Not sure why. I tried ...
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1answer
60 views

how to check the slope in a certain point in a graph in ltspice?

i have a graph in ltspice and i am trieng to find in which point the slope is -1 ? for example this graph : is there is a way to find out ? or i just need to guess ? thank you in advance ! ...
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2answers
37 views

how to plot two graphs on ltspice on the same y scale?

i want to plot more than one graph on ltspice , the first one shows the voltage vout according to vin , and the second one the derivative of vout to vin , but it shows the two graphs on two different ...
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1answer
44 views

How to plot a derivative in ltspice? [closed]

I want to plot the "derivative of V(out)/10". I get the following graph but this is wrong because it supposed to be negative (the blue graph should start from 0 and not 5.6 ), which means the graph ...
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1answer
37 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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17 views

Plotting pulse width or frequency of a pulse train LTspice

Maybe I'm demanding from the tool too much but I'm wondering whether the following possible in LTspice. I have a PWL file(time and voltage values) which can be read and plotted by LTspice. This is a ...
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1answer
38 views

Best practices for using subcircuits and hierarchical blocks in LTspice

I'm designing a series of circuits in LTspice and wanted to get some feedback on the accepted way to use subcircuits and hierarchical blocks. The LTspice manual is somewhat vague on these topics. In ...
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1answer
21 views

Plot Stepped Measured Data is disabled at Spice Error Log LTspice

I'm following the example from the top answer of this question. Here below I exactly do the same thing: But when I right open Spice Error Log (View -> Spice Error Log), and right click on a place as ...
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Decomposing a waveform in LTspice to view only the transient component

In electric-circuit theory due to superposition for an LTI system, the voltage can be thought such that it is sum of of a transient response plus a steady state response. For example below the ...
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1answer
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lt Spice simulation duplication error

I am new to using LT Spice. I have imported an operational amplifier. When I try to run a simulations response I received an error (shown in the screenshot.) It says Netlist Error: Duplicated ...
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1answer
21 views

LTSpice display issue on osx [duplicate]

I'm knew to this site spice so please be gentle :) I've installed LTSpice (LTspice XVII for OS X, Build Oct 25 2018, 14:56:22 US Pacific) on a MacBook Pro running macOS High Sierra 10.13.6. When I ...
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1answer
289 views

What does actually the “unravel branch wrap” option do to the phase plot in LTspice?

Below two Bode plots are identical just that in the second one the option "unravel branch wrap" is unticked for the phase plot: What does this option do to the phase plot?
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Finding expected outputs for a 4 bit SAR logic ranging from 0 to 1.8V (LTSpice)

I am having troubles getting accurate results for my 4-bit SAR logic schematic. I have tested different values to verify that my DAC works as expected. So I figure that there is something wrong with ...
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LTspice - using save/load bias with a parameter sweep

I have a circuit which has some hard time converging in a DC simulation. The circuit does converge nicely in a transient simulation when skipping initial condition calculation. Therefore, I've ran ...
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15 views

How to simulate an AC source function generator circuit?

Hi I'm trying to simulate this circuit on LT Spice, but I'm not sure what I'm doing incorrectly since it's not the graph that I want. Also how would I compute the phase difference between the input ...
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1answer
31 views

How to simulate this pulse in LTSpice?

A quick question, I have this pulse as an input to some device: I just need to simulate it in LTSpice. I have the values of voltage obviously, and I know how to simulate that fall time. I just need ...
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2answers
73 views

Creating a waveform which is abruptly changing from one frequency to another smoothly in LTspice

I want to create a sine wave with offset which is abruptly changing from 1Hz to 10Hz at a desired point in time without discontinuity. I tried and could only reach the following result: First of all, ...
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2answers
57 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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1answer
39 views

Whats the difference between bode plot linear and cartesian?

As in title, Whats the difference between bode plot linear and cartesian in LTspice? In both cases i get V(f) but the values differ. Which plot will give me values of voltage at given frequency that ...
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1answer
52 views

Simulation discrepancy in Qucs with 2N3904 transistor

I've been testing out a few circuit simulation applications and ran into an unusual issue with Qucs and the 2N3904 transistor. For a simple NPN transistor circuit with load resistor \$R_L\$, base ...
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1answer
48 views

How do I create a working bandpass filter in LTSpice?

I am attempting to create a bandpass filter in LTSpice. I am fairly new to the program, which is probably contributing to my difficulties. The filter I am creating needs to have a center frequency of ...
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2answers
49 views

Is there a simple way to quantize an input waveform in LTspice?

How can a 1V sine-wave input be converted to a staircase sine-wave with an 8-bit resolution for instance in LTspice? Or is this even possible? Can this be achieved without a complicated ADC circuitry?...
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LTSpice Error:Trouble converting curly brace notation

I load NCP1031 component on LTSpice but I got this error: Trouble converting to curly brace notation: Mismatched single quotes in ''V_V5 4_5V GND 4.5V{''.The circuit is proposed by its datasheet. So, ...
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1answer
18 views

Ltspice ac anlysis with dc offset

I am doing ac analysis of a simple passive RC low pass filter. The input is a 2 V peak to peak sinusoidal signal. R=1.2k and c=12nF. I want to add a 2.5 V dc offset to the input signal. When I change ...
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2answers
45 views

Implementing analog multiplexers in LTSpice and Cadence Virtuoso

Is there any model for Analog Multiplexer compatible with LTSpice or Cadence Virtuoso? A simple 2:1 multiplexer is implemented in LTSpice as a SPDT switch. So how to implement a 4:1, 8:1 or 16:1 ...
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2answers
55 views

LTspice- Huge current spikes across MOSFETs in full-bridge inverter

I have designed a simple full bridge inverter in LTspice. The outputs for voltage and current are as expected however I have huge current spikes across the MOSFETs which I am using as switches and are ...
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24 views

How can I force LTspice to redraw a plot during a long simulation?

Sometimes during long simulations, the LTspice plot window will display a yellow "broken" icon, and/or simply not render parts or all of the data. Sometimes the axis are missing, sometimes it only ...
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How to simulate memristor crossbar array in spice properly?

I am trying to simulate a memristor crossbar array. But I found the readout voltage is constant for 3x3 and 5x5. Theoretically, the readout voltage should decrease with crossbar size. I check the ...
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40 views

LTSpice Operational Integrator not Working

I'm fairly new to LTSpice and I'm having a hard time making this circuit to work. So I'm making an Operational Integrator but my Output signal doesn't seem to match my predictions. If I'm not ...
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Instrumentation Amplifier Output Voltage Questions

Ok, so I am currently trying to build a temperature sensor based Instrumentation Amplifier circuit using the AD8429 (data sheet link here). The schematic for my circuit so far is below: A very basic ...
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How can I save the output points of a circuit as wav file in LTspice? [duplicate]

Is it possible to save the output of an LTspice circuit output in wav format?
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1answer
71 views

Bug in LTSpice while moving component

Hi. I installed LTSpice in my macbook pro late 2011 with this specs: OS: Mac OS high Sierra 10.13.6 Graphic: Intel HD Graphic 3000 512MB RAM: 16 GB somehow I got a bug when i moved a component or ...
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1answer
31 views

audio, LTspice - crossover simulation problems

I am currently trying to design an x-over. The response of what I have spiced does not correlate to what I though would happen. Have I made any obvious mistakes? I want a Sallen-key HP/LP. That ...
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26 views

Singular Matrix: Check node warning

I'm trying to design a regulated power supply. When I try running the following circuit in LTSpice, I get the following error message: ...
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2answers
30 views

LTSpice Error: timestep too small

This is the error I see: This is my Simulation Command. What is the issue here?
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1answer
43 views

What is an expression for the output voltage?

simulate this circuit – Schematic created using CircuitLab Is this just a voltage divider principle and it boils down to sin(1000t)+sin(5000t) ?
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1answer
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LTspice XVII: Subcircuit pin names in Operating Point analysis

Is there a way to have subcircuit names show up in the Operating Point analysis? For instance, I have this test circuit: Here, the pins are named A and K for the opto's LED and C and E for its ...
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1answer
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LTspice on MacOS - empty library

On freshly installed LTspice on MacOS I have no libraries. In "Top directory is only /, but there is no way to edit this path, also in settings there is no tab ...
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1answer
56 views

How to add a reset after 4 clock cycles in LTSpice

I am trying to verify the output for 4 bit SAR logic. So far this is my schematic: These are my resullts so far: I am trying to add more to the PWL, which is what I assume I have to do, but the ...
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High Voltage Cascode with MOSFET LT Spice Simulation

I'm an electronics engineering student and want to develop a high voltage switch with normal Si N-MOSFETs. After some research, I discovered cascode switches for this application. Most of these ...
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1answer
39 views

LTC6994-2 signal inverted and time delayed

I use LTC6994-2 to delay and invert input signal. I want 2s delay between input and inverted output. However, this is what I get on the output: Green waveform is input waveform. Output (Blue ...
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1answer
60 views

LTSpice chassis ground or earth ground

I'm trying to simulate a circuit for a design I'm making. In a few parts of what I'm interfacing with uses relays that when closed will short a few power supplies to the chassis ground and in LTSpice ...
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1answer
278 views

LTSpice IV for OS X (oct 2, 2018 version) crashes on macOS Mojave 10.14

I downloaded the latest LTSpice IV for mac OS, I'm running mojave on a MBP. It is crashing in my setup, apparently as soon as it opens the plot window. The simulation starts running, but when it's ...
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3answers
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Voltage drop on string of constant-power loads: Simulation issue?

I've noticed something that seems odd to me in an LTspice simulation (see below). I'm trying to model a system with a number of identical devices which each draw ~11W (with negligible variation over ...
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1answer
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How is the sweep type affecting the Bode plots for the same AC analysis in LTspice?

When I do an AC analysis for the following circuit between 0.1Hz upto 20MHz, and by selecting "decade" in sweep types I obtain the following plots: But if I do exactly the same thing only this time I ...
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1answer
140 views

LTSpice simulation stalls after 100ms transient with 'Heightened Def Con'

I simulate a system of two mutually delay-coupled electronic clocks (DPLLs - digital phase-locked loops). This worked well and also in reasonable time so far. However, moving into a particular regime ...