Skip to main content

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 a very liberal license, it is lightweight, and isn't crippled in any way.

2,404 questions
Filter by
Sorted by
Tagged with
-1 votes
1 answer
53 views

How to simulate a current zero crossing in LTspice

I'm designing a flexible AC transmission system that utilises TSR.I'll need to use a voltage zero crossing and current zero crossing in my circuit to send to the microcontroller. I've being playing ...
0 votes
1 answer
37 views

Why is the amplitude of the output voltage affected by the resistance during resonance when LC is connected in parallel with a resistor in series

The following picture is the circuit I simulated. My question is, through theoretical calculations, the resonant frequency of this circuit ...
• 31
4 votes
2 answers
72 views

How to I add tolerance to an LTspice .lib electrical characteristic

I am currently trying to figure out how to add tolerance to my LM4040, ZVP2160, and 2N3904 components. I'm attempting a Monte Carlo analysis and use the ...
0 votes
0 answers
53 views

What should I expect and how can I simulate two PIN photodiodes in series?

I am trying to modulate the current through a PIN diode using another PIN diode. I want to do fast modulation, so I would like both of them to be in reverse bias. If I use the configuration shown in ...
-1 votes
1 answer
78 views

How to measure the 3 dB bandwidth of an opamp in LTSpice

I am interested to use an opamp with an exact 3 dB rolloff at 320 kHz for an sinewave (voltage swing) from -10 to +10 V. I think I need to do this using some resistors and capacitors on the feedback ...
• 815
2 votes
1 answer
94 views

LTspice issues with op-amp filter

I need to simulate in LTspice a wattmeter connected to a 800 V DC/DC converter (step-down) with silicon carbide (SiC) transistors. The wattmeter measures the voltage across the lower transistor (V_out)...
• 23
2 votes
2 answers
88 views

LTSpice simulation of Zener Diode Breakdown

I am trying to create a small circuit to read a voltage range of 0-12V using STM32F103 ADC. I have a simple voltage divider circuit as attached. I do have a 3.3V Zener to clamp the voltage at ADC to 3....
• 595
-2 votes
2 answers
66 views

N-MOSFET switching problem in LTspice

In this circuit as per theory it should switch. But it is not switching. Why it is happening.
• 35
2 votes
2 answers
75 views

LTSpice-MOSFET switching problem [closed]

Why is this happening in LTSpice? Is my circuit wrong?
• 35
3 votes
2 answers
84 views

How can i analyze the transient response of a circuit?

I have recently become interested in electronic circuit design and transient analysis of these circuits. Unfortunately, throughout my university life, we have only studied the analysis of RLC circuits ...
0 votes
1 answer
61 views

LTspice Error: Time step too small error

I want to simulate this circuit but in LTspice it shows this type of error. Is there a software problem or a problem in my design? I designed this circuit for Regen clamping High side switching for ...
• 35
1 vote
1 answer
38 views

LTspice behavioral model: Use a computed variable name as time input

Trying to run a LTspice simulation with a parameter computed (time250) as an input to timedelay on apulse voltage source. Any help with syntax or ckt correction advice get this error always Voltage ...
0 votes
0 answers
74 views

Why is there 2.27V on the drain terminal of M1?

I have a circuit I am making to either switch two capacitors C1, C2 in parallel or in series. The intended behavior is when V3, V1 = 0V, V2 = 5V; they should be connected in series and the opposite ...
1 vote
3 answers
54 views

Measurement Reference PSpice/LTspice

I have been using LTspice previously for my designs, recently I have encountered an issue. I have a design with a GND reference as seen in the picture and I want to measure the voltage across the 5 Ω ...
-1 votes
0 answers
42 views

LTSpice simulation circuit Amplitude doesn't like the real circuit problem

I built the function generator circuit on a breadboard. I applied a signal with an amplitude of 1.06Vpp and a frequency of 5MHz using the DDS 9851 and then sent it to the operational amplifier, AD ...
0 votes
2 answers
87 views

LTSPICE : incorrect behavior of bulk cap

I wanted to simulate a bulk cap for a 24V 50Hz smoothing to check my calculations but something is wrong in SPICE and I can't figure what: Blue is the cap current and it goes to 0 after the cap is ...
• 299
1 vote
1 answer
82 views

Filter cutoff frequency crossover

I'm designing a tone control stage for an audio amplifier I'm designing. I'm receiving a mono signal that is fed into 3 filters: Lowpass - 0:250 Hz Bandpass - 250 Hz:4 kHz Highpass - 4 kHz:infinity (...
0 votes
0 answers
36 views

LTspice syntax error no such function

I created a subckt model. It is working fine with ngspice. In LTspice 24.0.12, however, I am getting This is my source code: ...
• 657
3 votes
1 answer
94 views

How can I use LTspice to find Vmpp and Impp in a PV module IV curve?

I'm trying to find the PV parameters of a PV module IV curve with the following script: ...
• 31
2 votes
3 answers
56 views

Determing the line and load regulation of a Zener MOSFET regulator

I am working on a circuit involving a bridge rectifier, a smoothing capacitor, and a Zener-MOSFET regulator. I need help finding a mathematical representation of line regulation and load regulation of ...
• 33
2 votes
3 answers
100 views

LTspice resonant circuit simulation: Output not building up as expected

What changes should I make to get the output buildup continuously in the simulation, until I get some warning, maybe "simulation out of bounds?" What is this underlying frequency of around ...
• 3,156
0 votes
0 answers
52 views

Understanding the relationship between values in an LTspice transformer

I am designing an LTspice transformer based on these values.: 8.8 W, 12 V AC, @500m A Vout (no load) = 14.38 V @ Vin = 122.5 V Vout (@480 mA) = 11.60 V Datasheet for reference. What I am struggling ...
• 33
2 votes
1 answer
96 views

Transmission Gate in LTSPICE

I am trying to simulate a transmisson gate in LTspice but regardless of the state of the clock it keeps giving me the exact copy of input as an output. I tried inverting the clock with a inverter but ...
• 399
1 vote
0 answers
36 views

Half-Bridge with ISC060N10NM6_L1 - LTspice "time step too small" error

Currently, I am simulating my half-bridge model in LTspice while using the ISC060N10NM6_L1. However I am having an error ("time step too small"). I included my simulation model. What is ...
2 votes
1 answer
113 views

How do I vary the frequency of a signal source in LTspice?

I'm trying to test the bandwidth of a common emitter amplifier for an electronics practical using LTspice. I need to vary the frequencies from 10Hz, 20Hz, 50Hz then decade by decade up to 1MHz, using ...
1 vote
1 answer
51 views

How to Accurately Simulate a Wideband Bias Tee in LTSpice?

I'm currently working on designing a wideband bias tee and have been using LTSpice to simulate its performance. However, the results I'm obtaining seem too good to be true, and I'm concerned there ...
1 vote
1 answer
60 views

Singular Matrix error while adding filter capacitor across the load in 3 phase diode based rectifier

I am trying to simulate a simple 3 phase diode based rectifier circuit in LT Spice. By using a filter capacitor across the load I am getting a singular Matrix error as shown in the picture. The error ...
1 vote
1 answer
70 views

Arbitrary Behavioral Voltage Source : Its not acting as it should be acting

I'm trying to make a circuit involving Arbitrary Behavioral Voltage Source, and the value of my BV is V = V(vsin) > V(vtri) ? 12 : 0 This should make the output voltage only around 12V and 0V, but ...
• 13
1 vote
2 answers
105 views

Why is the LTspice simulation behaving differently in these identical cases?

Case 1: Capacitor initial voltage initialised using .ic command, IC not grounded. Result: Simulation is incorrect. Initial condition not being used. Case 2: Capacitor initial voltage initialised ...
• 3,156
1 vote
2 answers
145 views

Why is KiCad simulation different from LTspice simulation for this LC filter?

The following is a simple LC filter to remove AC noise: In LTspice this will generate something like this: Schematic in LTspice:
• 953
0 votes
2 answers
47 views

How to change polarities of input of voltage controlled voltage source in LTspice

I want to swap the input voltages of this VCVS: to be something like this: How do I do so?
2 votes
1 answer
67 views

Is there a fix/mod to accelerate drawing waveforms in LTspice

LTspice is very slow to draw the waveform window. This can be so extreme, that the software spends the entire time trying to rescale/redraw the graphs, especially for busy waveforms for things such as ...
• 22.8k
4 votes
1 answer
217 views

LT6268-10 Opamp Oscillation and Offset

Below is my Photodiode-OpAmp circuit that is configured as Transimpedance Amplifier. When I put both inverting and non inverting into ground, no signal is coming out. However when I connect ...
1 vote
1 answer
79 views

Modelling power transfer under saturation for 1:N current transformer in LTspice

A toroidal current transformer consisting of two half-toroids with air gaps, is clamped around an overhead 50 Hz AC power line carrying 50-300 A (i.e. a 1:N CT). It is used for energy harvesting. Is ...
0 votes
1 answer
99 views

Help to configure an LTspice PLL simulation

I never tried PLLs before and to gain some insight I'm trying to simulate CD4046Bg in LTspice where I want the output to phase-lock and follow the input signal. I tried so far the below: But I get an ...
• 1,468
0 votes
1 answer
59 views

Import transistor into LTSpice

I would like to import this transistor -> RFD16N06LE (datasheet: https://www.alldatasheet.com/datasheet-pdf/pdf/67811/INTERSIL/RFD16N06LE.html) into LTSpice; the datasheet has a PSPICE model ...
• 91
1 vote
3 answers
90 views

Decent MOSFET for a beginner to learn from?

I am relearning MOSFETs, but more importantly I would like to focus on building some basic circuits and learning practicality over theory. I have a BSEE but haven't spent much time outside of class on ...
2 votes
0 answers
38 views

Where should I take the measurement from to find the correct attenuation level of a resistive pi attenuator?

I am currently designing a resistive attenuator for an RF project I'm working on. I wanted to have several resistance combinations to obtain various attenuation levels (1-8 dBs). When I calculate the ...
1 vote
0 answers
63 views

Can this oscillator possibly work?

I am trying to build a crude RF oscillator. My first attempt, though it simulated fine, disappointingly did not oscillate when soldered together. So, to debug this, I reduced the simulation example ...
• 716
0 votes
1 answer
98 views

How can I simulate an RF signal as received by an antenna in LTspice?

How can I simulate an RF signal as received by an antenna in LTspice? I am designing a simple HF RF receiver and want to test it via LTspice. Can I simulate an RF signal as: A pure voltage source, ...
• 1,307
2 votes
1 answer
110 views

Why did I get different simulation results for the same transistor model in LTspice?

The following is my FM transmitter circuit. In the first simulation, I auto-generated a symbol for BFQ19S. Replace the auto-generated symbol with the one from default NPN. In the second simulation, ...
• 953
-2 votes
1 answer
132 views

Is there any way to speed up simulation in Ltspice? [closed]

The following is my FM transmitter circuit. It takes about 1 minute to simulate. In real life, I want to use this BFQ19SH6327XTSA1 from Infineon instead of 2N22222. (link datasheet) and download link ...
• 953
1 vote
2 answers
66 views

Beat frequency - Square signal

This question comes from this one, LTspice - Beat frequency: It appears that when I did a FFT of two sinusoidal signals, there was no what is called beat frequency. When I do the same exercice with ...
• 2,530
1 vote
1 answer
105 views

Does the FFT in LTspice not work properly?

I wanted to do an FFT of a square signal in LTspice. Here is the simulation: Here is the result of the FFT through R4: There is no reason to have frequencies below 100 kHz according to theory. What ...
• 2,530
1 vote
3 answers
104 views

LTspice - Beat frequency

Here is the theory from wikipedia: Here are my summation of sin on LTspice: The frequencies are 100 kHz and 120 kHz on the FFT. There is no frequencies at (f1+f2)/2 and no frequencies at (f1-f2)/2. ...
• 2,530
1 vote
0 answers
53 views

Need help analyzing sability of op-amp in a current source in LTSpice

I have to perform stability analysis on an op-amp (AD8671) which is being used as an op-amp in the circuit attached. I am using LTSpice to perform this. My approach is to give a 1V AC small signal at ...
2 votes
1 answer
62 views

I am Seeking Help to Adjust DC Motor Simulation Parameters in LTspice for Accurate Current Modeling

I'm relatively new to LTspice and motor diagnostics, but I have managed to build a PWM-MOSFET control circuit for a DC motor. My goal is to simulate this project to evaluate potential ripple currents ...
• 63
-1 votes
2 answers
72 views

LTspice simulating varying capacitance in cap-to-voltage simulation [closed]

I am interested in simulating the increasing output voltage and the end of this circuit when the parameter C1, changes according to a list of increasing capacitance values. So far I have managed to ...
• 11
1 vote
1 answer
63 views

How does the leakage inductor distribute over multiple coupled inductors?

I am working in LTspice with a triple coupled magnetic inductor. I chose the factor of coupling to be 90%. L_1 is 1000uH so the uncoupled energy should be 100uH. How does the 100uH energy distribute ...
• 103
0 votes
1 answer
61 views

Iterative Simulation LTspice Model using Python

I'm new to python. I have a python code to simulate my LTspice model. I need to change the on time in the pulse parameters and I need a large number of simulations for at least 100 different Ton. So I ...
• 21