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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1answer
387 views

LTspice error reading a downloaded model

I'm downloading a model for an n-channel MOSFET, the DMG6968U-7. This is the SPICE code: ...
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1answer
27 views

How to store custom ltspice symbols/schematics in a subfolder?

I made a simple inverter INV.asc and associated symbol file INV.asy, which I am using in my top-level test file, ...
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1answer
223 views

Power over time for RC ish circuit in LT spice

I have a simple circuit in spice that I put a 0-5V step function into. So basically as square-wave going in. Then I can get my current and voltage waveforms out, or do some math to get power. But I ...
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0answers
20 views

ac analysis of circuit in LTspice

T want to AC analysis of circuit , where source is modulate which is going to generate AC signal of varying frequecy and varying amplitude according to V1(frequecy) and V2(amplitude) with respect to ...
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1answer
62 views

How to increase output voltage of an op amp well above the supply voltage

I have a circuit which produces a (not high speed) signal between 0 and 9 volts with an adjustable slope, and I would like to increase this output voltage to between 0 and 200 volts, which keeping it ...
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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 ...
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55 views

LTspice subcircuit with behavioral voltage source

I'd like to use behavioral voltage source in subcircuit block, as showed below: With block "comp": But when I try to simulate it doesn't work and gives mi this message: Someone could explain what's ...
5
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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 ...
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2answers
942 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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1answer
33 views

How to flip LTspice voltage controlled switch so that it opens at threshold voltage? (versus close)

I am trying to figure out how to tell the VSWITCH of the LTspice program to open after it crosses the threshold voltage and close when it is below (with hysteresis). Normal behavior is that with Vt ...
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2answers
326 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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3answers
6k views

Fourier transform - LTSpice

Is it possible to get the Fourier transform in LTSpice? For example I'd like to plot the Fourier transform of the following signal: $$s(t)=A \space sin(2\pi f_0t)$$ Can you attached a LTSpice ...
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1answer
442 views

How to install a scr model in ltspice

I have downloaded an scr model file from this website and pasted it in the same folder as that of my .asc file. But ltspice still shows unknown subcircuit called for the scr present. What am I doing ...
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2answers
102 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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1answer
46 views

Getting following error in LTSpice simulation : “Too few nodes…”

I am doing simulation using LTspice and getting error as Too few nodes. I am using three external library components/parts. Could you please help me to identify where I am missing. Thank you. D1 -...
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2answers
823 views

LTSpice: how do I pass to a function a component name as parameter?

Good morning all. I am implementing a subcircuit in LTspice, and I want also to modify the plot.defs to calculate some quantities with the voltages/currents inside the subcircuit. Thus, I will have a ...
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0answers
65 views

How to reduce simulation time for large radio frequency signals (400 MHz) in LTSpice?

I am simulating circuit for input frequencies 10 kHz to 400 MHz, but its takes long time while simulating the circuit, so is their any alternative way to reduce simulation time and increase speed? ...
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1answer
37 views

Add LTspice IV library to LTspice XVII

I have an external library which works fine for LTspice IV. To add this external library, I simply overwrote (added) the corresponding files in the lib folder in the installation directory. Hence, I ...
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2answers
104 views

Why does the output of this opamp change my analog signal?

I am trying to make an inverting Op-amp circuit in LTSpice where I can invert an analog signal without any gain on my signal, I want the signal to stay the same but inverted. I have followed the basic ...
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1answer
486 views

LTSpice Op Amp Model Accuracy

I am trying to match an op amp (OP27) to its data sheet while doing some stability analysis tasks in LTSpice. I am following the video provided here (http://www.linear.com/solutions/4449). However, ...
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1answer
55 views

LTspice Vs Matlab - Power electroncs

What are the advantages in power electronics of Matlab in comparison with LtSpice and vice versa ? Thank you very much and have a nice day ! :D
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0answers
25 views

Simulation LTSpice Miller plateau and reverse recovery diode

I would like to do a simulation in order to better understand the losses in switching power supply. I m trying to a simulation with the following circuits : I'm working at very high frequency in ...
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2answers
47 views

Why does LTspice resistor noise disappear when setting value with .param?

When performing a noise analysis in LTspice of a 1kΩ resistor, a noise level of 4nV/rtHz is simulated. However, if this resistor value is set to 1kΩ using .param, ...
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1answer
400 views

LT-SPICE subcircuit programming

I want to create a SPICE subcircuit file for an electronic component. I have found the Verilog A code for the component, I want to know how to convert the Verilog A code to LTSPICE compatible ...
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1answer
48 views

THD analysis of an arbitrary expression in LTspice

Is it possible to perform .four THD analysis of an arbitrary expression in LTspice? It works seamlessly with simple expressions like ...
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0answers
49 views

Total harmonic distortion vs frequency

Is there a way to plot the variation of THD of a circuit due to a frequency sweep of the input signal? I use LTSpice. Cheers
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1answer
7k views

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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2answers
6k views

ltspice, time step too small, microchip operational amplifier

I am trying to simulate a LDO with Microchip MCP6001 operational amplifier in LtSpice. With other OA simulation is ok, but with all Microchip models, the same error: ...
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1answer
425 views

Appropriate models to model magnetic components in LTspice and what are the pros and cons?

I'm looking for appropriate models to model magnetic components, mostly transformers and perhaps for chokes as well, for use in LTspice. I've heard briefly of some models, like Jiles-Atherton-model (...
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2answers
305 views

LM317 maximum current output as a voltage regulator

I built the following circuit in LTSpice using LM317. With a current load at the output, stepping from 0.1A to 1A, I noticed the output voltage collapsed at around 800mA. This is a surprise, since I ...
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1answer
48 views

LTSPICE P-Channel MOSFET

I'm learning LTSPICE and am very confused by the results coming from playing around with P-channel MOSFETs. I created a very complete test of P-channel and N-channel MOSFETs, and all the N-channel ...
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2answers
467 views

Can I have two (or more) different symbols for the same LTspice schematic? How?

I have two components in my top-level schematic and noticed that the schematics of these components are actually the same. To avoid any duplication of changes done to these subcircuits, it would be ...
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2answers
94 views

Why is this capacitive circuit not working in both multisim and LTspice

The voltage at the top most node of this circuit should be the average of the input voltages. Vtop*CT = C1*V1 +C2*V2 +C3*V3 where CT = C1+C2+C3 I get 0V instead. UPDATE Thanks for the help. I ...
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0answers
15 views

ltspice: assign list of values to .param

If I want to do a simulation for a set of .param values I can do .step param R1 1k 10k 1k. But this generates a set of ...
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1answer
347 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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0answers
103 views

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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4answers
643 views

LTSpice: How to offset the start time in a transient simulation?

I see how to set the total run time for a transient simulation, but what if I didn't want the simulation to start at 0s? For example, if I have two voltages sources that are stepping at offset times ...
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0answers
24 views

Can't find definitions of model irfs4010

I'm trying to run on the LTSpice the circuit below. It's the circuit of a Boost-Converter. When I try to run, LTSpice shows the message "M1: Can't find definition of model irfs4010". Sorry if i'm not ...
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1answer
51 views

How to overcome current drop in circuit with high inductance value?

I have a very simple circuit that uses a switch to switch between a resistive loop and inductive + resistive loop. Whenever I switch from resistive load to inductive load, the current of the source ...
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3answers
666 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 ...
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1answer
159 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
176 views

LTspice table function

how does a table function work in LTspice? In the LTspice library, it says, table(x,a,b,c,d,...): Interpolate a value for x based on a look up table given as a set of pairs of points. I don't really ...
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2answers
57 views

LTspice .param variable component selection

Update: In case I could not explain myself clearly, I am reparaphrasing what I want to achieve. Let's say I will have 8 opAmps. Their symbol is opamp2 and their values will be LM741 with ".lib lm741....
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1answer
23 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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1answer
89 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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1answer
435 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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1answer
91 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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0answers
104 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
204 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
773 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 ...