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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8 views

Lser of capacitor not equivalent to a separate inductor in LTspice?

I just noticed a strange issue in LTspice and I am wondering what I am doing wrong. This is about capacitors with series resistance and inductance: Example 1: A simple bandpass. Behavior seems ok. ...
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23 views

Problem simulating electrolytic capacitor at high frequency

I am simulating a circuit in LTspice in which I use an aluminum electrolytic: C=100µF, Rser=0.25, Lser=5n Due to some other components, I now see an L-C resonance at several GHz in AC simulations, ...
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30 views

LTspice simulation does not work like the real circuit

I designed a Colpitts oscillator which uses a BC238B transistor. When I set the circuit up on breadboard and PCB, it works flawlessly fine and I receive a sinusoidal signal at the output. When I ...
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1answer
20 views

How to pass parameters to subcircuits in LTSpice with the include statement?

Let's say I create a block with resistors R1 and R2. I want to use this block as a subcircuit in other designs. The typical way to pass in the values for R1 and R2 is to right-click on the block and ...
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69 views

Why is the op-amp not able to amplify this voltage? It's a straight-forward non-inverting configuration with ideal op-amps(LTSpice simulations)

So I have the following configuration (pretty straight forward right?) But following are the waveforms of V_induced(the voltage to be amplified) and V_induced_amplified. As you can see, the voltage ...
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What is the value of voltage controlled switch to demodulate the PAM circuit

What is the possible value of V3 (voltage controlled switch) and the command to demodulate PAM signal?
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38 views
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Should I be concerned about this RMS current?

I have designed this buck converter and I am pleased with result - 97% efficiency. Although I calculate it only if I use average current, not RMS (my formula: Vout * Iout / Vin * Iin). Should I be ...
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1answer
177 views

Can someone help me make this circuit work?

I am trying to implement the circuit described in this paper in LTspice. The circuit is shown below: The paper claims that the circuit can be used to measure the resonant frequency of the coupled LC ...
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22 views

Are the following two LTSPICE statements equivalent?

.meas tran vin_pp pp V(Vin) from=1m to=4m .meas tran vin_pp pp V(Vin) from 1m to 4m When entering the statements in the dialog box, the equal sign is not used. I am also having trouble getting the ...
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47 views

How accurate is this LTspice model of common mode signals?

The 0.9MHz voltage source at the bottom is what I want to use to model common mode noise on the signal. Is this the correct way to think about this? I am going to use this to do some analysis on that ...
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29 views

LTspice not recognizing model embedded in schematic

I am trying to use some third party models in a simulation and getting an error saying "model not found" no matter how I try to reference them (.lib, .inc or pasting model file directly into ...
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487 views

High-Side NMOS for Buck Converter?

I'm working on designing a buck converter, so I've been using LTSpice to simulate the circuits. However, it seems that I'm misunderstanding something. My understanding is that one should not use an N-...
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54 views

LTspice - Inaccurate Center-tapped Full Wave Rectifier Results

this is my first post so I apologize if I do not follow any sort of convention. I have researched how Center-Tapped Full Wave Rectifiers should work and from what I found, when the turns ratio is 1:2, ...
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33 views

Ltspice digital look up table

Can't find digital LUT model (look up table) for Ltspice. I'd like to have some configurable LUT. For my application, I need 5 in / 1 out. I tried to create one myself, but it's not that easy, as I ...
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1answer
51 views

LTSpice outputting the incorrect voltage reading?

I have analysed this circuit by hand using both mesh and nodal and always come to the same voltage reading. However, when I simulate it in LTSpice, it does not match. The V1 node reading should be 9....
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45 views

At LTspice, are there any methods to change the values at once?

I want to make capacitor value C1=C2=C3 and change it at once. I know the .STEP PARAM command, but it needs at least two values. I want to set all values equal, and change it simultaneously. Like this....
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58 views

How exactly does LTspice resolve circuits

How exactly does LTspice resolve circuits ? Suppose a simple RC circuit (or more simpler if needed). How LTspice will resolve the circuit ? Why the time step is so important ? Have a nice day :)
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24 views

Saving LTspice colors & drafting settings on CrossOver (Wine)

I run LTspice XVII on mac OSX using CrossOver (Wine), as I prefer having access to the toolbar and menus in the Windows app that are absent within the native mac app. It works well, except that ...
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1answer
36 views

I`m getting into a trouble with ltspice to get a voltage gain of BJT(NPN)

The picture above is the problem. I solved the problem like bellow I tested this circuit by ltspice expecting that voltage gain shows 0.09615. But the result of Vout was just flat like dc output. ...
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16 views

LTspice .MEAS doesn't unravel branch wrap

When doing AC analysis in LTspice, there is an option to unravel branch wrap (i.e. phase un-wrapping). However, if we use .MEAS to find magnitude and phase, there is no option to unravel branch wrap, ...
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1answer
40 views

LTspice simulation of microphone preamp

Can someone help an idiot understand why this plot has dual traces? The node is between C2 and R7. I have replaced an electret microphone with an AC source. I don't know how accurate this is, so any ...
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22 views

How can I use the model DMOS NMOS in a .mod file shown in the picture below?

I'm trying to implement a CS amplifier with the model DMOS NMOS, but I'm having difficulties with how to import and use the given model DMOS NMOS in my circuit, I've been trying to look for tutorials ...
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12 views

Create spice model from S parameters file 2 terminals

I want to do a simple design using this amplifier. Though it is simple, I would like to somehow simulate it to fine tune some components. The manufacturer provides a ".S2P" (here) file with ...
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1answer
43 views

Use simulation model in LTspice

I want to simulate a circuit that uses this transistor using the popular simulator LTspice. When I download the simulation model from the link I get a .zip file containing the following two files: ...
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97 views

Measuring the hysteresis losses via LTspice

I simulated the B-H curve of a random transformer. I would like to compute the hysteresis losses per period by computing the area of the curve. I know how to time integrate a set of points via a spice ...
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1answer
37 views

LTspice - Create a subcircuit and modify its own parameters

I have created a subcircuit on LTspice. Here it is: It has a lot parameters that I would like to adjust. Her is the netlist: Just have to create the symbol and it is done. Here it is: Nevertheless ...
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48 views

I want to get voltage gain in BJT by using LTspice

This is the task that I want to solve using LTspice: I solved the problem like this: But when I did this in LTspice, something`s different: Please, someone tell me what the problem is and share a ...
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1answer
91 views

Operational Amplifier Output Stage Biasing

I am trying to bias my op-amp output stage using diodes. I am using a current source for the bias current but later I will replace it with BJT current source. However, it doesn't seem to work. ...
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2answers
65 views

In parallel current sources with capacitors

I have to get the correct equation of multiple parallel non-dependent current source in parallel with capacitors, as i seem to find the correct solution, the resulted simulation in LTSpice shows ...
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2answers
99 views

How to properly design LC bandpass filters?

A little disclaimer. Electronics is a hobby to me so I learn it on my spare time. This leads to certain knowledge gaps that professionals might not have. I want to build a good filter using SMD ...
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1answer
70 views

Op_Amp as an integrator

[ I designed a simple op amp and now I am trying to make it work as an integrator as shown in image 1. The output voltage waveform looks fine for a sine input as I am getting negative cosine as shown ...
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66 views

Op-Amp not working as a integrator

I designed a simple 2 stage op amp. Now I am trying to make it work as an integrator as shown in image 1. The frequency response as shown in image 2 is as expected and I am operating between the ...
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66 views

Current limiter using 2 bipolar junction transistors (BJTs)

I want to know where are the input and the output of this circuit in LTspice. I also need the values I should use for the resistors and the transistors in order to see clear results for current ...
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1answer
49 views

LT Spice cant find definition of model

I have designed a operational amplifier in Lt spice as shown in the 1st image. I changed the name of the BJT models as I wanted to change the beta value. 2nd image shows the symbol of the op amp 3rd ...
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1answer
33 views

dc-dc step down converter model and the command of a JFET in LTspice

I am trying to reproduce this command circuit of a JFET semiconductor: and there are many components I am struggling to reproduce in LTspice. For instance, for the dc-dc converter, does LTspice ...
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44 views

Buck boost inverter design with current mode

As a project, I should design inverting buck boost converter without using IC. I designed somehow the converter but not optimized it yet since I have no proper drive. I am planning to set output of ...
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18 views

Is there a way to download extra components for LT spice on a MacOS?

I am new to LT spice and I have been using it on MacOS (not recommended) I am struggling to find advice on how to download Spice models and add them to my components library. Following the same steps ...
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25 views

How to show opamp noise contribution in LTspice .noise calculation

When doing system noise calculations using LTspice using the .noise instruction, I can plot the total output noise and I can plot all the individual noise contributions to output noise from all ...
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1answer
27 views

SPICE model for PMBFJ309

Does anyone knows where I can find SPICE model for PMBFJ309 or similar? I searched a lot and could not find. If anyone knows, could you please share the link.
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46 views

The behavioral voltage source in Ltspice, is there a physical circuit that we can use?

I am trying to make a physical circuit of the circuit shown below: All the components can be found easily like the resistors, capacitors, bjt except the behavioral voltage source. So can anyone tell ...
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1answer
39 views

LTSpice simulation problem with calculus of power

I am trying to determine the optimal resistance of a simple circuit which would maximise the power harvested. The calculus of V(Y) is funtionning But the one of PRMS and PAVG is not I changed my ...
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1answer
42 views

How to implement this scenario for a stable opamp integrator?

I want to make a circuit using opamps and passive components where the input is a pulse train and can be with a frequency between 100kHz upto 3MHz and the duty cycle can be 100% or down to 1ns ON time....
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2answers
64 views

In-Series current source equation solving

I'm an electronic newbie, i was simulating this circuit on LtSpice and i found the result below, i tried with different methods (Kirchhoff's laws, Millman theorem, superposition) but i failed to have ...
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1answer
70 views

What are the resistor values that I should use in order to get 38dB gain? [closed]

I have build a common emitter-common collector multistage BJT amplifier. I want to get an output gain of 38 dB under the conditions of 8 ohms load resistance, 6 volts, 25 mVpp input voltage signal. ...
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1answer
55 views

Common-mode choke on LTSpice

Can someone suggest to me how to select a three-phase common-mode choke with self and mutual inductance in LTSpice?
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35 views

AC sweep on H bridge circuit

I built a H bridge circuit and I'm struggling with the analysis part. Below is the H bridge circuit I built. A brief description of the circuit: V1 and V2 both send inverse PWM signals and U1 and U2 ...
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22 views

AC sweep and Dc sweep help in Lt spice?

I built a H bridge circuit and I'm struggling with the analysis part. Below is the H bridge circuit I built .A brief description of the circuit: V1 and V2 both send inverse PWM signals and U1 and U2 ...
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1answer
34 views

FFT analysis of summed signal in LTSpice

I know that simulating FFT analysis of current/voltage across a single element via LTSpice is quite straightforward. I have simulated the summation of three distinct currents in the time domain. I'd ...
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1answer
73 views

How to implement a power multiplexer in LTSpice?

I need to implement what I will describe as a power multiplexer for use in testing other circuits in LTSpice. The idea is to be able to switch a range of loads and sources into the output of the ...

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