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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43
votes
5answers
57k views

How do you simulate voltage noise with LTSpice?

Is there a way to setup a voltage supply with voltage jitter/noise? I want to experiment with filtering out noise on various voltages etc. but not sure how to configure LTSpice to create a noisy ...
25
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5answers
41k views

LTspice: Vary a resistor's value over time

I want to simulate the load regulation of a power-supply. I'm sure I remember being able to vary the value of a resistor over the course of a simulation in LTspice, but I can't remember how. Anyone?
15
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5answers
19k views

LTSpice Automation

I have a battery-powered boost converter and I'm attempting to measure the maximum input (battery) voltage droop under various load conditions of high current draws (different duty-cycles/...
15
votes
3answers
4k views

Why doesn't LTSpice predict this op-amp oscillation?

I'm developing a circuit to act as an electronic load for bench testing power supplies. An earlier question about how to test this circuit received several very useful answers and can be found here: ...
14
votes
1answer
2k views

LTspice sinusoidal voltage source with offset much larger than amplitude broken?

I've been troubleshooting an analog circuit and have just come to the realization that Sine Voltage sources at mV are broken. Here is one that is supposed to provide a 1mV 1Hz sine wave on top of a ...
13
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3answers
15k views

Why is my simple boost converter giving me such a high peak output voltage?

I am trying to understand switch-mode power supply fundamentals through a simulation in LTSpice. I wanted to build an excruciatingly simple boost converter circuit following a teaching model often ...
12
votes
3answers
13k views

How to view and customize beta of a transistor in LTspice

If I need to set beta to a custom value, is it possible to make a customized transistor with a beta of my choice? In other words, can I edit a ready or generic transistor's beta and save it as a ...
12
votes
1answer
10k views

How to plot “voltage drop” across a specific component in LTSpice?

In the above circuit I can only be able to plot |Vr1+Vc1| = V1 in green plot and Vc1 in blue plot. I use the voltage probe in LTSpice and click on the lines to obtain the plots. If I click on the line ...
12
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2answers
27k views

How to use .step param with more than two parameters in LTSpiceIV

I need to do three transient simulations with different values of certain resistors (conveniently called R1 and R2) in each. What I mean to do exactly is this: Sim. 1: R1 = 1 k\$\Omega\$, R2 = 10 k\$\...
12
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2answers
26k views

Why does LTSpice say that my “Matrix is singular” for this ideal-transformer circuit?

I'm trying to do find the voltage over R1 in the following circuit, where L1/L2 is an ideal transformer. LTSpice complains that the "Matrix is singular". Why? I've tried to play around with lots of ...
10
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1answer
759 views

Issue with parallel resistors in LTSpice

I'm trying to build a reactive load box, so I can run a guitar amplifier without a speaker. It's basically a device that simulates the impedance/frequency curve of a relatively high power speaker. I ...
9
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2answers
7k views

LTSpice simulation of rectifier slows down after short time

I have the following simple circuit set up in LTspice: Blue is on the output of the transformer and green from the rectifier. If I don't include a capacitor this works fine and the simulation goes ...
9
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1answer
2k views

LTspice: How can I show multiple probes with waveforms using stepping parameters in different colors?

I'm using LTspice IV (4.23I) and I am using the .step command to vary the capacitance of a capacitor, so that I can see multiple waveforms for a single probe. If ...
8
votes
3answers
2k views

What's the junk at the end of my FFT in LTSPICE?

Why do FFTs have junk on the high frequency end? Suppose I go to simulate this circuit in LTSPICE: simulate this circuit – Schematic created using CircuitLab Where the LTSPICE sine and ...
8
votes
1answer
3k views

How do I achieve XY mode on LTspice?

I have two node voltages that I wish to plot against each other, similar to the XY mode on an oscilloscope. How do I achieve this via LTspice? LTspice only plots quantities against time.
8
votes
1answer
5k views

How does the Arduino Deumilanove Auto-Reset Function work?

I'd like to hear some explanations as to how the Arduino Duemilanove resets the ATMega328P over USB through the FTDI FT232R transceiver. I know it involves the IDE playing some games with the DTR ...
8
votes
3answers
315 views

What are the calculations to do in practice to estimate beforehand the noise seen on the output of this op amp circuit?

I would like help with understanding something better, but am not trained in electronics so please bear with me! I am trying to make a simple circuit to take a {-10V ... +10V} signal from a function ...
7
votes
2answers
2k views

How to control rise time of output of LTSpice's Voltage Controlled Switch?

I have a RC delay circuit as input into a Voltage Controlled Switch in LTSpice. It's working the way I want, except I can't figure out how to shorten the rise time of the signal that emerges from the ...
7
votes
1answer
278 views

LTSpice: What breaks KCL in .op but not in .tran simulation?

Simple BJT rheostat circuit, with a couple of resistors R1a and R1b representing the two parts of a potentiometer. Simulated in LTSpice IV using a part not suitable for this particular application and ...
7
votes
3answers
1k views

Discrete opamp design

I am working on modifying SG acoustics SGA-SOA-2 op-amp. The goal is to make it work on 32 \$ \Omega\$ headphones load, and use more common transistors. What I did was: Replaced all transistors ...
7
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1answer
3k views

How to change the top directory in LTspice?

I installed LTspice in C:\Program Files, and when I go to "search components", the top directory is C:\Documents. How can I ...
7
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2answers
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,...
7
votes
1answer
6k views

LTSpice - Printing resultant parameters based on expressions

I'm designing a circuit but I'm computing the values of components based on a set of design values. For example, ...
7
votes
1answer
1k views

Has LTspice been extended to support the modified-Chan, non-linear hysteretic model for coupled inductors (transformers)

I'd like to figure out how to simulate coupled, non-linear cores using the included modified Chan model in LTspice and I'm specifically interested to know if LTspice has ever been extended to support ...
7
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0answers
4k views

Automate LT-SPICE? [duplicate]

I'm running a lot of simulations in LT-Spice, and I need someway to run them all either sequentially or at the same time. I was going to use Python, but I'm not entirely clear on how I would get ...
6
votes
3answers
6k views

How to plot sliding average in ltspice?

I would like to plot a sliding average of some voltages and currents. Ideally I would just add a new trace with some expression, but all expressions that I found so far only operate on single values. ...
6
votes
2answers
4k views

LTSpice: How to vary resistances in a simulation depending on the value of a voltage?

I am trying to implement the Hodgkin-Huxley model for simulating neurons using LTSpice. One feature of this model is that the resistances at any given time actually depend on the transmembrane voltage ...
6
votes
2answers
1k views

How can I link a component's current to variable resistor value in LTSPice?

In LTSpice I want to implement an LDR resistor which changes due to the current passing through an LED. I want the current through the LED (D1) to vary LDR. I want to use the LED's current in an ...
6
votes
2answers
8k views

Is there a spice directive to export waveform data in LTspice?

http://www.linear.com/solutions/1815 The above web-page explains how to export the waveform data to a text file. You basically run the LTspice simulation, clicking on the waveform window, go to ...
6
votes
2answers
2k views

LTSpice: Can I vary schematic temperature over time?

I'm trying to simulate a temperature sensing schematic with a latching function (meaning that the schematic should go to overtemperature mode at let's say 75C and go back to normal at 50). I can do a ...
6
votes
1answer
709 views

N-MOS real-life gate threshold voltage (Vgsth) lower than claimed

I faced with a paradox that N-MOS transistor real-life Vgsth (gate-to-source threshold voltage) is significantly lower than claimed. It should be about 1.7 V (and the simulation confirming that ...
6
votes
1answer
918 views

How to change the temperature of sub-circuits in LTSPICE

I have subcircuits of a solar cell (resistors and diodes) in LTSPICE. I want to connect the solar cells (sub-circuits) together. However, each solar cell has a different temperature. I can set the ...
6
votes
1answer
7k views

Simulating real world transformer with LTSpice

I'm studying LTSpice, and I'm playing in transformer simulation. I want to modelize a real world power line transformer in a reasonable way: I mean I don't need an exact simulation of some specific ...
6
votes
1answer
400 views

Simulating Chua's circuit in LTspice with a saturating transformer-based nonlinear resistor

Chua's circuit is one of the simplest circuits known to exhibit chaotic behavior. It consists of resistors, capacitors, an inductor, and an active nonlinear resistor. One implementation of this ...
6
votes
1answer
4k views

Unijunction transistor in LTspice?

I would like to simulate a simple oscillating circuit involving an unijunction transistor. I do not find such component in LTspice so I figure I need to import one. Could please show me step by step ...
6
votes
2answers
748 views

Op amp circuit stability in linear regulator circuit

I am trying to design a stable linear regulator using MOSFET and op amp. Schematics is shown below: I am using LTSpice for simulations. This circuit is mostly for educational purpose: I want to ...
6
votes
2answers
9k views

Parts tolerance simulations in ltspice

I just recently found this tutorial (and various other places mentioning a similar technique) when trying to evaluate how one of my circuits behaves when using real world components with real world ...
6
votes
2answers
179 views

Help figuring out what is the limiting factor on the noise level in this analog optocoupler circuit

I am trying to build a circuit that takes a {-10V ... +10V} analog signal and outputs the same {-10V ... +10V} voltage but galvanically isolated from the input. The idea is similar to that of digital ...
5
votes
3answers
859 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.
5
votes
2answers
19k views

How can I model a relay in LTSpice IV?

I would like to use a 12V relay in my LTspice circuit, however there is no relay in the component list. How can I do? Relay model: SRD-12VDC-SL-C
5
votes
1answer
365 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 ...
5
votes
3answers
665 views

LTSpice: how to setup sinusoidal or exponential voltage source?

My textbook proposes to calculate power for the voltage source which has sinusoidal or exponential waveform. Probably my question is very silly, but I really don't know how to input textbook's ...
5
votes
2answers
482 views

Common source amplifier using mosfet: Why is my Id dependent on my Rd?

Since I'm (trying to work) in the saturation mode, the following formula should be valid: Since Vto is a static parameter it shouldn't change, same for K. And Vgs is 2 as determined by the voltage ...
5
votes
2answers
16k views

How to define the initial charge of a capacitor in SPICE

I would like to simulate a circuit with a capaciot in LTSPICE. In the first hand, I have tried to charge the capacitors in a period of time. However, the charging current is very high and I am not ...
5
votes
3answers
389 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 ...
5
votes
2answers
629 views

Charging one capacitor with another capacitor in LTspice

I'm trying to simulate charging of one capacitor \$C_2\$ by another \$C_1\$ using LTspice. Following the derivations in this video, I found that in the end, both capacitors \$C_1\$ and \$C_2\$ should ...
5
votes
7answers
14k views

LTSpice (mac) How can I display the current in the schematic?

I want to simulate a circuit and display the current directly in the schematic. However I am only able to display the voltage. Here you can see an example where someone actually displayed the current ...
5
votes
1answer
9k views

SPDT in LTspice

I'm currently new to using LTspice as a circuit simulation software. Right now I'm trying to check if the IC (BD6221F-E2) that I included in the program is working. The process of making this IC is ...
5
votes
2answers
3k views

Why does the LTspice op amp stability tutorial recommend open loop analysis?

I have performed a hand analysis on an amplifier circuit that I am suspicious of, and I am still suspicious, so I want to validate my hand analysis with LTspice. I found this tutorial online: http://...
5
votes
1answer
875 views

How to (.step) change bjt/fet/opamp models in simulations in LTSpice?

Is there a way to change bjt/jfet/opamp model in simulation in LTSpice (similarly to changing parameters with .step command)? I would like to compare different bjt/jfet/opamp models, run a number of ...