# 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.

968 questions
Filter by
Sorted by
Tagged with
15 views

### import new component into LT Spice with .cir file

my desperate attempt to simulate a circuit led me here. I have a low noise amplifier which has a HEMT as its transistor. (ATF38143). I have been trying to create a component in LT Spice and came ...
17 views

### Hall effect sensor model in LTSpice

I am working on hall effect based current meter and I run into some troubles running my simulation in LTspice. To be precise I am no sure how to accurately model hall effect sensor. In less accurate ...
3k views

### Why doesn't the output of the opamp change with the source impedance?

The datasheet of this opamp says the input impedance is typically 100Meg. So I expect the voltage gain to be halved with a source resistance of 100Meg. But the following simulation doesn't reveal that ...
51 views

### Circuit simulates in Falstad but not in LTspice

I'm having trouble simulating what should be a simple circuit in LTspice. I am designing a simple PWM-regulated power supply, but I'm running into problems when I try to simulate it. When I simulate ...
43 views

### How to model real transform in Ltspice

Here is two different models of transformer which are equivalent I know how to model the transformer on the left but I would like to model the one one the right. It is more intuitive for me. I don't ...
17 views

### Drive signal (duty cycle) calculation for PI compensator

I am trying to simulate an inverter with 4 ideal switching devices in LTSpice. I have the compensator working, however I don't the correct equation in terms of calculating the duty cycle. What I ...
42 views

### Simple CMOS switch with weird voltage in LTSpice

I am new to all this, so please forgive me, as I feel the answer to this must be so simple. I tried to build a basic CMOS switch. It has a supply of 5 V. There are periodic pulses of 5 V supplied to ...
45 views

### A fundamental question about crossover distortion

Following shows the input output waveforms to illustrate crossover distortion: The supply rails are indicated as if it is a dual supply(+V & -V). I then tried to simulate this in LTspice as in ...
44 views

### Simulation problem with AD9632 opamp

So I'm trying to simulate the AD9632 op amp in LTspice. The spice model was downloaded from the official analog devices website. However the simulation results are not as expected. Since the gain is 3,...
33 views

### OTA LTSpice model help

(This is my first post go easy on me) I'm trying to use an OTA to simulate a floating voltage controlled resister like explained here, but I cannot for the life of me figure out how the mota model ...
35 views

### Questions on piso shift register and simulating in LTspice

After my previous question, I attempted to simulate an 8-bit "parallel in serial out" shift register in LTspice as follows: The above schematic is not very readable due to its size so below is the ...
30 views

### Frequency response across component in ltSpice

How do I find frequency response across a component not referenced to ground.
55 views

### Why is this D flip flop not working in LTspice?

Below is the circuit: I expect the Q1 Output should follow the clock since the DATA is set to one(5V), but the output is zero: I looked for many examples but couldn't figure out what is wrong.
50 views

### LTspice IV How can I get round value with 4 point digit?

First of all sorry if the title aren't fully describe what I want since I'm not native Eng speaker , In short I start taring my self on electronic using LTspice IV , since I don't want high ...
66 views

### Nodal analysis for resistive circuit

Given the following circuit: I know that I1 = I2 + I3, but what would be the relationship between I2,I3,I4, and I5? I would assume if there are 5 unknowns, we'd ...
24 views

### Connecting terminals to transformer on Power Inverter circuit LTSPICE

I am simulating a Power Inverter circuit using LTSpice, but I am confused as to where the corresponding terminals from the resistor and mosfets go. I am trying to simulate this circuit: Based on the ...
32 views

### AC Decade Sweep LTSPICE Error

The output plot for Vo/(Vg) is not outputting a smooth curve. I chose a decade sweep with starting frequency 1 Hz and end frequency of 10 GHz. Why is the plot not smooth? I am pretty sure I built the ...
21 views

### How to create LTspice hierarchical blocks/sub-circuits/custom components? “Missing schematic of the hierarchy: ”

I have been using LTspice with groups of components copied and pasted from previous models and this is getting quite ridiculous. I want to be able to create hierarchical schematics but every time I ...
37 views

### Simulating Power PMOS using LTSpice

I have a power P-channel MOSFET that can produce a max of -34 A and whose datasheet does not include parameters W or L. How can I model this PMOS without W or L if I only have $R_{DS_{on}}$ and \\$...
65 views

### Question regarding to LTspice diode simulation :

While simulating using .op analysis for the forward bias of a diode in LTspice, it showing the source current Iv1 in negative sign. But, all the other currents are in positive sign. What does it mean?
56 views

### Perfect component on LTspice

Is this possible to have perfect components in LTspice? No parasitic inductance, no parasitic capacitor, no resistor, etc? Is it not possible is it possible to make a model and model it with no ...
34 views

### Simulation of an asymetric half bridge not working

I m not able to simulate an asymetric half brige circuit :( I m new on LTspice... Here is the simulation which is really simple ... When I simulate it, I am surprised to not have 400V across the ...
22 views

### LTSpice Simulations require netlist flattening on higher simulation counts?

As in my previous question mentioned, i am doing bulk simulation with predefined component parameters for a given amount of runs. These are calculated and written to the file via python scripts i made ...
25 views

### LTSPICE how to use the TSTOP and TSTART in Subckt?

For years I am using an automated potentiometer in LTSPICE that changes the position of the wiper from one side to another proportionally with time, I specify that time in two variables used in Subckt ...
37 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, ...
63 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 ...
369 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 ...
35 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 ...
60 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 ...
54 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 -...
66 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? ...
53 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 ...
106 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 ...
70 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
32 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 ...
50 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, ...
52 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
55 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 ...
18 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 ...
26 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 ...
52 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 ...
50 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 ...
62 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....
25 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. ...
141 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 & ...
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 ...
100 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 ...
47 views

### Lt-Spice doesn't give me all the information

Here is my LT-spice simulation of a simple circuit. I need to find the voltage across R6, but Lt-Spice doesn't give me that information. Does anybody know why this is or if there is something wrong?