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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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LTSpice IV for OS X (oct 2, 2018 version) crashes on macOS Mojave 10.14

I downloaded the latest LTSpice IV for mac OS, I'm running mojave on a MBP. It is crashing in my setup, apparently as soon as it opens the plot window. The simulation starts running, but when it's ...
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Voltage drop on string of constant-power loads: Simulation issue?

I've noticed something that seems odd to me in an LTspice simulation (see below). I'm trying to model a system with a number of identical devices which each draw ~11W (with negligible variation over ...
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28 views

How is the sweep type affecting the Bode plots for the same AC analysis in LTspice?

When I do an AC analysis for the following circuit between 0.1Hz upto 20MHz, and by selecting "decade" in sweep types I obtain the following plots: But if I do exactly the same thing only this time I ...
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LTSpice simulation stalls after 100ms transient with 'Heightened Def Con'

I simulate a system of two mutually delay-coupled electronic clocks (DPLLs - digital phase-locked loops). This worked well and also in reasonable time so far. However, moving into a particular regime ...
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29 views

How do you adequate select correct number of data points and binomial smoothing for correct FFT in LTspice?

I'm trying to simulate what a spectrum analyzer (SA) would see from a LISN, to get a rough know how. Previously solved: In LTspice can I convert the units of an FFT which by default seem to be shown ...
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In LTspice can I convert the units of an FFT which by default seem to be shown in dBV to dBµV?

In LTspice can I convert the units of an FFT which by default seem to be shown in dBV to dBµV? Cause of reason: The reason for this is that I've a modeled a LISN in LTspice where I want to simulate ...
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68 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 ...
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21 views

LTspice parametric sweep: how to force the simulator to continue with the next step?

I'm running transient simulations as I am sweeping a couple of parameter values (resistances, capacitances) to give a first hint about what range of values make a certain circuit stable. In addition, ...
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71 views

How do you model differential inductor in LTspice?

I wonder how I can model a differential inductor in LTspice? I've an inductor that has half the turns on one side and the other half on the other side. It's intended to be used in a bridge tied ...
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34 views

Auto-numbering components in LTspice

I'd like to re-number the components of my LTspice simulation from left to right and top to bottom to make the schematic more presentable. For example, in the circuit below, I'd like R44 to be R1, R50 ...
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42 views

Zener Controlled transistor series voltage regulator using LTSpice

I have been designing a Zener Controlled transistor series voltage regulator circuit using LTSpiceXVII. MMSZ5232BT1G is the zener diode (5.1V). For various DC voltages (6V, 8V, 12V, 16V, 20V, 24V and ...
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40 views

Voltage controlled switch always closed in simulation

simulate this circuit – Schematic created using CircuitLab I have made the above (useless) schematic in LTspice. This after running into issues with a full schematic. The idea is to let e pulse ...
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45 views

555 Timer IC Simulation in Eagle

I am currently designing a circuit in Autodesk Eagle which requires a 555 timer IC. The timer may be any 555 chip, such as an ne555, tlc555, or lm555, or even one of their 556 variants, but the lm555 ...
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21 views

Bandpass filter severely attenuating input signal in passband

I've designed a 3rd order chebyshev passive bandpass filter with 10% BW and center frequency of 10kHz. However, when I feed it a 10kHz sine wave to the input, it immediately gets severely attenuated, ...
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56 views

How can I convert PSpice model into LTSpice Model?

I would need to simulate these two MOSFETs ino LTSPICE but I have the Spice Model IPW65R019C7 Its PSpice model its insiede Nchannel CoolMos C7 https://www.infineon.com/cms/en/product/promopages/power-...
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33 views

LTspice simulate

I try to do simulation with a saturating inductor of flux model. And when the flux function is simple such as k*x etc, the simulation can run correctly. When this function becomes more complicated, ...
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93 views

Second Order Passive RC Low Pass Filter Doesn't Have -6dB at cutoff Frequency in LTSpice

For Second-Order RC filter the cutoff frequency is: $$fc = \frac{1}{2\pi \sqrt {R_1C_1R_2C_2}}$$ I have taken R1 = R2 = R = 1K Ohm and C1 = C2 = C= 0.1591 micro Farad. So the cutoff frequency comes ...
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50 views

Open loop Flyback simulation LTSpice

I am designing a flyback converter with an input voltage of 220Vrms and a 600V output with a current of 0.1A. To begin with, I am considering a 310V DC voltage input, and simulating the open loop ...
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39 views

Infinite Negative Magnitude in LTSpice

I am trying to make a current Dependent current source LTspice and I finally got it to compile, only to get a magnitude of -1.#INFdB on my readout. The dependent sources on this program are very ...
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2answers
53 views

Problem with setting initial voltages in LT Spice

I was trying to set an initial voltage for a capacitor I was modeling in LT Spice, and I tried using the command .ic V(Vc)=20000 (Vc is the node directly after the capacitor, with ground on the other ...
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1answer
64 views

Power amplifier simulation and real time experiment mismatch problem

Thanks in advance to anyone who will take the time to read my first post here. At present, I am doing a simulation of a power amplifier in LTSPice. The schematic and relevant files are uploaded in a ...
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32 views

Can you change the parameters of all of a certain kind of component in LT Spice?

I was wondering if there was a function in LT Spice that I don't yet know of that would allow you to either select a bunch of components, or all of a certain kind of component (capacitor, resistor, ...
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Issue using pspice .lib in ltspice - Unknown Parameter

I received an unencrypted PSpice model of a TI Boost Converter (TPS43061) and I am trying to use it in LTSpice but I'm getting the following error and I'm not sure what I can do about it. Unknown ...
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51 views

Low output voltage on buck converter

I am making use of the LM2678 adjustable version switching regulator in the design of a 5.5V buck converter. I made use of the design equations detailed here: lm2678 datasheet For the following ...
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1answer
66 views

Why is this MOSFET Differential Pair On on the Right-Hand Side?

Could someone please explain to me both the qualitative and quantitative analysis of the following MOSFET differential amp circuit, to explain why Vs = -0.5 V and the Right-Hand MOSFET is "on"? EDIT -...
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66 views

Read a value of open circuit or GND

I'm trying to make a circuit that have in input a "not connected" or "GND", and the output is a function of input. For example if there is no connection, the outpur is 3.3V. If the input is connected ...
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40 views

Does LTSPICE automatically include avalanche parameters in its power dissipation measurements?

Does LTSPICE power calculation window like this take into consideration MOSFET avalanche parameters and include them into the overall average power value? That particular image is for a resistor ...
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101 views

Simulation of 3-phase inverter and bootstrap capacitor in LTSpice

I'm trying to simulate three phase inverter for BLDC. Because of floating potential of high side MOSFETs I need to use bootstrap capacitors. After looking at some datasheets/forums I thought that I ...
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163 views

3-Phase Inverter simulation

I'm trying to simulate a 3-phase inverter for BLDC(PMSM) in LTSpice. The problem is that drain current is way too high and also phase voltage isn't right. **New image *One leg If I put one source(...
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101 views

LTspice simulation of AD8421 instrumentation amplifier giving incorrect output voltages

I am trying to run a simple simulation of an instrumentation amplifier (AD8421, model from here) running on a single supply, but the output does not seem to be correct. The screenshot below shows the ...
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116 views

LTspice (XVII) Use component instance name as a parameter

I am trying to to simulate a ferroelectric capacitor using simple schmitt triggers subcircuits : simulate this circuit – Schematic created using CircuitLab I would like to pass {R1} as a ...
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61 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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69 views

Importing transistor spice model to LTSpice not working

Using LTSpice XVII. I want to import the Diodes Incorporated ZXTP19020DG model. The SPICE model from their web site is: ...
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51 views

lt spice model error

I am trying to run a simulation for a power amplifier design. I am using On Semi NPN and PNP transistors. I have Spice models from OnSemi for these parts. ===== Here is an example of the model from ...
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178 views

LTSpice is frustrating me. Why isn't this Class C amplifier working? I can't get a sinusoudal output

I've been trying to research how a class C amplifier works, and it makes perfect sense to me, but I'm having problems getting it to function in LTSpice. I have the latest LTSpice version (XVII with ...
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48 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 ...
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161 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 ...
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85 views

TTL NAND logic circuit

how can find the maximum fan-out of the TTL-NAND gate using LTSpice ? i tried to solve problem by hand, but the problem how to find fan-out using ltspice
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Importing LT SPICE schematic design into Altium Designer 18

I'm working on designing a front-end data acquisition board for signal analysis, and have completed the schematic in LT SPICE. Now I want to import the schematic design into Altium Designer 18 in ...
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39 views

LTSpice LTM4622 test fixture “ignoring empty pin current” error

When I run .tran .5m startup for the LTM4622 the simulation runs properly , but I get the error shown below. I'm wondering whether I should worry about it, since the simulation results line up with ...
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96 views

Why are my p-channel mosfets cutting off in LTSpice even though Vgs is negative?

I'm running into a weird bug. Part of me thinks that it's LTSpice that's wrong, but that seems unlikely. I'm working on the circuit below, to be able to switch between feeding my voltage regulator ...
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48 views

LTSPICE - Simulation Portability

Does anyone know of a comprehensive source of information on LTSPICE directories, libraries, the Control Panel - Sym & Lib Search, model locations, etc. as they relate to simulation portability? ...
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46 views

How can I simulate limits of active components?

I am using LTSpice to simulate an energy harvesting circuit, so I am very careful with small leakage currents and losses. This circuit is all discretes (Diodes and FETS) and passives. Is there any way ...
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97 views

General Feedback Theorem - Spice model and loop gain

I am implementing the General Feedback Theorem (Prof. Middlebrook, 2006) in LTSpice, using the example given in the Spice folder. I used it to calculate the loop gain in a simple voltage follower ...
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2answers
94 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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1answer
53 views

How to change the delay variable Td for a tline component in LTspice?

I want to change the transmission delay-time Td (see picture) of a tline-component in LTspice as a function of time during simulation. From my understanding, I ...
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1answer
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Node with two different voltages at the same time - Two branches (voltage source+resistor) in parallel - LTspice

I simulated the following circuit: Why is Vu=7.5 V? I expect there to be an error because Vu=5=10 at the same time. The current in the two branches is the same, thus (R1=R2): $$Vu=R_1 i+V_1$$ $$Vu=...
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1k views

Why does this circuit start at a very high value?

I have a capacitor connected in series with a current source. But the voltage remains at 1TV. Why is it not increasing? Also, in general, if I don't want to connect the other end of the current ...
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2answers
74 views

Inserting an unused voltage source in LTspice messes up transient results

This took me three days to figure out. Consider this simple circuit in LTspice: Looks pretty innocent. The output is a 1V sine wave, as expected. Going to View->FFT, setting number of data points to ...
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114 views

Schmitt trigger with 741 op-amp not behaving as in simulation

I am implementing a Schmitt trigger using the circuit shown below. This circuit consists of one LM741 op-amp, which acts as an asymmetrical Schmitt trigger with a single power supply. According to ...