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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2
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4answers
12k views

How to integrate a signal in LTSpice?

Is it possible to integrate a signal in LTSpice and plot the result?
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/...
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?
4
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2answers
382 views

A question about heating of a slowly turning off MOSFET

I have an N-Channel MOSFET IRF530 with its datasheet used in the following circuit: When turned on it passes 2.5A current. So I first wanted to make some calculations to check whether I would need a ...
4
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3answers
2k views

How to fix this LTspice error

Below is an H bridge inverter circuit model I came across in net: I'm getting Singular matrix Iteration error when I try to run this. If I delete the circuit on the right things work. Or if I ground ...
2
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3answers
547 views

Miscalculation of current for a pure inductive circuit in LTspice

A 10mH inductor is coupled to a 10V 60Hz AC supply as in the below circuit: Solution of the current amplitude for this pure inductive circuit is given as: But when I simulate this circuit in LTspice ...
43
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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 ...
15
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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: ...
6
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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
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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 ...
3
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3answers
479 views

Why does DMM show AC and DC current when source is a battery? (How to calculate power in this case?)

The circuit is an altered Joule Thief of my design that is driven by an AA or AAA battery. I’m observing the current at the battery anode with my DMM in series. (Extech EX330) This circuit is ...
8
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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.
4
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3answers
15k views

ltspice .param if statement

Super simple question here. Is it possible to use an if statement in a .param LTSpice directive? If so, what is the syntax? Shown below does not function. Note that the .step function can not be ...
2
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1answer
1k views

Using a single phase induction motor equivalent circuit in LTspice

I was planning to simulate a circuit which will control a single phase induction motor in LTspice where mains is 230VAC 50Hz. In my previous question, I failed to find an example: Modelling a "...
4
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2answers
2k views

A question about negative dB in LTspice

Above is a screen-shot from an LTSpice simulation. It is a freq. response of an LC tank circuit with a 5V sinusoidal AC source. When I plot it, the y-axis is in dB. When I look at the voltage it is ...
2
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2answers
104 views

Ideal LC circuit decays over time in LTspice

I was trying to simulate a transformer without a load, and setting an initial condition to observe how the energy will flow from the primary to the secondary circuit. I realized that the energy will ...
1
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1answer
412 views

Simulation of a class E power oscillator using LTspice

My goal is to understand and design a class E power oscillator. To this end, I am trying simulate the following schematic using LTSpice. Circuit topology and the design values are extracted from the ...
0
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2answers
2k views

LTspice default rising/falling times of pulse edges

Above is how I set up a pulse in LTspice. When I set the rising and falling edges as zero or if I do not register any value, in that case LTspice automatically sets the rising and falling edge ...
0
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0answers
191 views

How to do switching noise analysis of dcdc on LTSpice

Background : In one of my board i have used LT8471 as DCDC , as my cards being analog cards, i tried maximum to seperate the power network and analog chain from noise, my initial problems with dc-dc ...
0
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1answer
139 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
57 views

My calculation for an RC circuit are not agreeing with the LTSpice simulation

I am doing calculations for an RC circuit to create a first order low pass filter. The input is a 5V peak periodic square wave with a 10kHz frequency. The resistor is 220 Ohms and the Capacitor is ...
12
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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 ...
11
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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\$\...
0
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1answer
10k views

LTspice “could not open library file” for a third party amplifier

I'm trying to use INA129 in LTspice. So first in TI's page I go to Tools & software and under the model download the file called: INA129 PSpice Model (Rev. B).zip In this zip file there are files ...
6
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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. ...
2
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3answers
5k views

Making a Triangle wave on LTSpice using LM741 opamp

I'm trying to get a 1kHz, 15V triangle wave on LTSpice. For that, I'm using the following design: So far, my Square Wave has the desired frequency and amplitude, but my triangle wave has a lower ...
8
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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 ...
7
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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 ...
5
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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
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7answers
13k 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 ...
4
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1answer
4k views

LTSpice, MAC97A8 TRIAC model, Vgs error

I'm having some difficulty getting LTSpice to like a TRIAC model. The specific error it throws is "Missing model definition for VGT-0.65". The trouble is that VGT is a subcircuit parameter, not a ...
4
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2answers
10k views

How to make LTSpice sub-circuits available globally?

LTSpice Hierachy block can not be found if it is not in current working directory. I am using this tutorial to create sub-circuits in LTSpice: http://www.audio-perfection.com/spice-ltspice/...
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2answers
4k views

How to create Spice / LTSpice repeatable damped sinusoid

Is there a more elegant and/or simpler method to model a repeating, damped sinusoid from SPICE or LTSpice rather than chaining the damped SINE sources in series? Below is a schematic and the ...
14
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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 ...
8
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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 ...
6
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1answer
707 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 ...
5
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2answers
8k views

Adding Photodiode to LTspice

I am very new to LTspice. I would like to ask "How can I add a photodiode in the Ltspice?" Is ideal photodiode (or any specific) model already included in the LTspice or do I need to create third ...
5
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1answer
2k views

How to model a noisy Zener diode in LTSPICE?

I'm trying to simulate a white noise generator of the Zener diode style. I'm going with current amplification, rather than the more traditional voltage amplification just because. My problem is that ...
4
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2answers
215 views

Cannot predict closed-loop gain of this amplifier

This is the circuit I am currently analyzing: (link to LTSpice file) I am trying to predict each stage closed loop gain and overall gain (with all loops closed). First thing I did is calculate DC ...
4
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1answer
765 views

How do I plot noise gain of an op amp circuit in SPICE?

How is an AC analysis of the noise gain of an op amp circuit plotted in LTspice? This is a follow-on question to a prior question here: What is noise gain, really? And how is it determined in the ...
4
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3answers
2k views

Why 60% overshoot with 55° phase margin?

UPDATE: Based on the answers I received, I got this working beautifully. There's a full outcome report in one of the answers below. I'm working through the design of an electronic load, basically a ...
4
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1answer
2k views

Why am I getting negative base current in LTSpice simulation?

When I was trying to bias an NPN transistor I noticed that the base current Ib is negative in LTSpice. So for the sake of simplicity I only apply voltage to the base-emitter junction. As you see in ...
3
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1answer
5k views

How to make an ideal diode model in LTspice

I would like to make an ideal diode model and have tried to achieve this using different settings in the .model statement, but there is always a voltage drop. I would like to make an ideal diode with ...
3
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1answer
723 views

LTSpice showing negative transistor power

I'm using LTSpice to model a LC oscillator, driven by a NPN transistor. When I used the power calculating function on the transistor, LTSpice indicated that during part of the cycle the power ...
3
votes
1answer
17k views

Simulating SMPS with ideal switch in LTSpice?

Yes, this in a portion of a homework assignment (hence the idealized and slightly asinine problem statement). Aside from solving the circuit (which I have done), I am supposed to simulate the ...
3
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1answer
826 views

LTSPICE: How to display traces automatically when press Run Button?

I have a question related to LTSPICE. Some of the examples placed in Educational folder have this feature (i.e. when I press Run button, automatically some traces appear). I analyze example, but I don'...
2
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6answers
8k views

How do I update LTspice IV for macOS?

On an iMac and a Macbook, both running macOS Sierra 10.12.6, I have installed the latest LTspice IV (Build Oct 3 2016, 14:49:11 US Pacific), which prompts me to update on launch. Attempting to do so ...
2
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1answer
2k views

LTSpice divergence between AC analysis and transient analysis for low frequency gain

A simulation is done in LTSpice (version 4.23k) There is an inverter: Fig.1: schematic 1mV small-signal input. AC analysis is run. Low frequency gain (Vout/Vin) is 20.69 dB (10.82 times). ...
2
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1answer
3k views

Using the .step command to step a parameter of a transistor model in LTspice

I read this document and I want to step the β parameter of a transistor for the below circuit(to see it bigger please left-click on the image below): Here is the model of the transistor and BF is the ...
2
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2answers
12k views

LTSpice D flip-flop not working

I'm an absolute beginner with LTSpice; my first test circuit uses a few D flip-flops: four of them as clock dividers (to divide the clock frequency by 16), and then 3 as delay blocks (to delay the f/...