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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Function Generator IC in LTspice - IC8038 / XR-2206 / MAX38 models, where can I find ? Or any alternative IC?

I am looking for IC 8038 / XR-2206 / MAX38 such function generator Spice models. I cannot find it anywhere. Where can I find or could you please suggest any alternative function generator IC in ...
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583 views

LTSpice: Get linear results using .meas command

Another quirky LTSpice question. I am measuring input impedance and using a .meas directive to get the impedance at specific frequencies: .MEAS AC Zi_freq1 FIND V(in)/I(v1) AT=10k When I right ...
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33 views

Impedance in LTspice and current plotting

I wanted to try a test simulation on LTSpice to understand few things. I have a RLC parallel circuit and I wanted to see how the impedance varies according to each one of the components (very easy but ...
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LTspice .TRAN UIC simulations with initial conditions as .IC directives

Starting from this question a doubt arises about the use of (global) .IC directives for 'branch currents' in LTspice (or maybe just SPICE) Consider the .TRAN card with UIC flag. From some test done it ...
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Ratio detector FM demodulator

The aim of the exercise is to design a ratio detector FM demodulator circuit. This is what I did in LTspice: I'm not sure how to check if the circuit is designed correctly. Below characteristics: FM (...
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1answer
33 views

Problem Running a Subcircuit in LTSpice

I am trying to design an Li-Ion battery charger and I am using an LM317 chip. I created a symbol and subcircuit file (LM317.sub) but LTSpice cannot find the subcircuit file. I am not sure why so ...
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1answer
114 views

Appending plots in LTspice

The single most important thing I miss in LTspice is the ability to plot things of multiple runs on top of each other. Cadence Virtuoso calls that "Append Plot". What I mean: I want to plot ...
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2answers
50 views

Recreate “Voltage gain vs Frequency” graph of Op-Amp in LT Spice

I am trying to recreate the "Voltage gain vs Frequency" graph of the LT1037 Op-Amp in LT Spice. According to the datasheet page 6 the graph looks like this: - Trying to recreate this in LT ...
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How can I determine PD for given impulse, based on transient thermal impedance for BJT?

I have (selected) a BJT to work with rectified mains application. Transistor is PBHV9560Z (600 V, 0.5 A PNP) https://assets.nexperia.com/documents/data-sheet/PBHV9560Z.pdf Under normal operation ...
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How can I change the standard .jft .bjt .dio .cap files in LT spice XVII

I tried adding a model to one of the standard.jft located at C:\Program Files\LTC\LTspiceXVII\lib\cmp (actually I was updating the standard.jft files from LT spice wiki, if you haven't done this you ...
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Calibration of response of electronics : LTSpice [closed]

I would like to calibrate my electronics. Row signal is something like pulse-A, width is 40nsec. When I input this signal to preamplifier, output is something like pulse-B. I would like to calibrate ...
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34 views

Importing Third Party Models in LTSpice

I am trying to import the 2N3904 NMOS transistor in LTSpice but the program is not allowing me. I have pasted the model name in the spice schematic as shown below. The error message is : "cannot ...
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LTSpice transient simulation of LC circuit

I've a question about the LTSpice simulation of the following simple LC circuit driven by a DC current source. The first simulation (A) looks good from point of view of initial conditions for either ...
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426 views

Questions regarding a comparator circuit coupling to an analog switch

This is directly related to my previous question, so it requires to first have a look at that. And the below LTspice implementation is based on Andy Aka's answer. The following circuit works in ...
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65 views

Why all voltage drop across NMOS MOSFET in ngspice

I am new to the ngspice simulation and when I run a circuit into ngspice, it drops all the voltage across a mosfet but this is not the case when I simulated the same circuit into LTspice. Any help ...
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63 views

Setting current source as active load in LTSpice

I don't understand what Parasitic Properties: This is an active load means in LTSpice provided as an option in the current source configuration window. I plotted ...
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1answer
52 views

Start an ac simulation at f=0Hz

I would like to know please why is it that I can't start an .ac LTSpice simulation at f= 0Hz. I would like to know the DC impedance (or the equivalent resistance of my circuit that also contains ...
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How can I model this common mode choke in circuit in LTspice?

How can the common mode choke in below diagram used in LTspice? By an inductor or transformer? How should be the circuit drawn in LTspice? I want to use this to filter out CM noises for single ended ...
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1answer
118 views

ltspice, simulate negative resistance, avalanche effect

I found some nice circuits here as a pulse generators http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html The author shows some scope pics and films from real world.. ...
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60 views

MOSFET voltage is opposite from what I expect

I have this circuit on LTspice. The voltage from the 12V seems to rise when the 5V is falling. What am I doing wrong?
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How to add transistor model to LTspice? [duplicate]

So, I'm an absolute beginner at LTSpice(I just started today). I want to know how to add the model of transistor(say model ZTX300 or BC108) to my schematic. I can't find the model in the standard.bjt ...
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230 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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4answers
45 views

LTSpice sweep resistance

I would like to plot the power obtained by this simple recovery circuit (UR1eff^2/R1) according to the value of the resistance R1. But as it is a sinusoidal function, it takes the average value of the ...
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SSHI circuit on LTSpice

I've been trying to get an SSHI circuit running on LTspice for several days now (see below schematic). My problem is the following: the simulation (.tran) stops after a hundred milliseconds. Being a ...
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1answer
133 views

How to use an encrypted HEX file in LTSpice?

I have downloaded a model of a MOSFET from ON Semiconductor and have a problem with it. The "model" looks like this: ...
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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 ...
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78 views

How to measure high frequency with an oscilloscope without loading circuit down too much?

I am experimenting with building a high frequency common emitter circuit shown here. It operates at 144MHz and it should have around a gain of 4. Here is the simulated circuit. I do not have any load ...
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LTSpice BJT Model Help

I am new to LTSpice and I was trying to make some experiments with BJTs. In particular i was trying to model a npn with VbeON = 2V. From the the ltspice site i found that the built in potential of the ...
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1answer
40 views

Error in resonant converter simulation

I designed a closed loop resonant buck converter using voltage mode control and simulated on PSIM. Here is my circuit:- This gave correct results. Now I want to design an input filter so I simulated ...
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Calculation results depend on simulation time (LTSpice)

I am trying to simulate a circuit with several neonbulbs. And I have notified that the results I get depend on the simulation time described in the '.tran' command. An example is in the picture below. ...
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How to use multiple WHEN statements in LTSPICE

Here is my problem: I am trying to measure 3 different params when multiple conditions are met. Here the part of the code that works ok (just manipulating some params) ...
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1answer
77 views

Help with 144Mhz small signal amplifier not amplifying

I attempted to build a single transistor amplifier to try and increase the voltage signal coming from a Si5351 module, set to 144 Megahertz. My primary goal is to increase the voltage about 3 to 4 ...
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LTSpice - Inductance simulation

Welcome back on this subject : I would like to simulate an inductance which varies linearly in function of the current which flows through it. Suppose : $$L(t) = I_{L}(t)$$ In the simulation for ...
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264 views

Approximating the dirac delta function on LTspice to find the impulse response of a high pass filter

I have an assignment which requires me to find the impulse response of a high pass filter on LTspice. In order to do this the question suggest feeding a Dirac delta function as an input to a simple ...
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4answers
138 views

dB scale in LTspice

I have a question about the dB scale in Ltspice. As far as I know it uses 1 of the unit (so 1V in case of Voltage) as a reference and then plots the dB value, which is defined by 20*log(V/Vref). (So ...
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Unable to simulate AD8232 SPICE model in LTSpice

I downloaded the SPICE model of the IC from the website. I can put a link to the webpage if anyone comments that I should, I am not because the last time I did so my post was flagged. I am putting a ...
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2answers
49 views

Simulate Cree XLamp XB-D LED LTspice

I want to simulate a a white power LED from Cree in LTSpice. I searched for a LTSpice model and Cree provided one. By simply putting in this model in LTSpice I get this characteristic. I do not ...
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57 views

LTSpice Error: Timestep too small error

The circuit that I am simulating is a Vishay PTC thermistor model number PTCTL7MR100SBE. I have a timestep too small error when trying to simulate. The link for the SPICE model. I tried running the ...
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1answer
56 views

LTspice Measure Phase

i am working with LTSpice simulation. And i am creating a bodeplot of an special circuit with the AC Simulation. How can i use the meas. command to measure the amplitude by -135° phase? I already ...
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1answer
70 views

LTspice - Simulation of a variable inductance

I would like to better understand how LTspice works with the variable inductor defined by using the flux through it. I have some troubles to understand why according to the above post the formula of ...
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1answer
78 views

RLC simulation with initial condition - what is wrong?

I measure the currents in the RLC system, I gave the initial condition to the LTspice program. The schematic in LTspice looks like below: However, the current comes out in kiloamperes: For ...
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2answers
63 views

LTspice simulation doesn't agree with predicted transfer function

I am trying to create an integrator in LTspice that I will use as a subcircuit in a signal chain later, but can't get the simulation results to agree with my theoretical calculations. I derived the ...
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1answer
186 views

This SR latch built with 180nm CMOS does not work in ltspice. How do I fix its behavior and parameters?

EDIT: I copied over the latch from another larger model that had Vdd defined, but missed it when copying over the design. However, after adding in Vdd, I still run into this confusing issue where the ...
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2answers
43 views

Help understanding the SPICE input impedance - why does it seem lower than I expect?

I am attempting to model a very simple common emitter amplifier for 144Mhz (2 meter HAM band). I found a LTSpice model for a nice RF transistor (MPSH10, 650mhz Ft) since jellybean transistors like the ...
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23 views

Any recommendations for gas discharge tube mathematical modeling references?

Any recommendations for gas discharge tube mathematical modeling references? Lieberman and Lichtenberg (2005) Principles of Plasma Discharges and Materials Processing (see @AdilMalik 2020-12-21 ...
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1answer
3k views

LTspice: Is there any way to access .measure results from within a subcircuit?

I have a subcircuit in my LTspice schematic. It appears as a schematic block. Within the subcircuit's schematic there is a .MEASURE statement. How can I view the results of this .MEASURE statement ...
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37 views

How to simulate a composite video input signal in ltspice

I want to simulate this video driver circuit (i think it's called that) in ltspice I found this design from this very nice video: https://www.youtube.com/watch?v=lqSiMKwfZsY by the videolabguy. To ...
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61 views

SPICE modeling gas discharge tube using state machine and behavioral resistor

A gas discharge tube (GDT) is a state machine which transitions from a high impedance ("normal") state to a low impedance ("glow") state when the potential across its terminals ...
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2answers
294 views

Comprehensive SPICE guide

I am using LTSpice for simulation, but I am finding that I have to look through many different online sources to find what I am looking for e.g. the section on analog behavioral modeling here http://...
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1answer
426 views

Some questions about a magnetically coupled circuit

Below the RLC circuit on the left side by the help of a periodic impulse generator V1 generates periodic damped oscillations with a certain frequency, and the resulting oscillating current couples to ...

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