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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Obtaining dynamic resistance of a zener diode in LTspice

Please left-click to enlarge Above is a circuit where: D1 is a 10V(breakdown) zener diode, V1 is a voltage source which varies from 11V to 5OV DC and R1 is a 1k resistor. My aim is to identify the ...
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54 views

Designing an High Amperage, Low Voltage AC Voltage “Breaker” for Model Train

I’m trying to build a simple circuit that acts as a "voltage breaker" – meaning that if a voltage exceeds a certain threshold, analogous to a (current) circuit breaker it will open a circuit. There ...
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43 views

Schmitt Trigger does not go to ground

i would like to create simple circuit to drive an computer fan (12V, 0.5A) is the temperature is above 42 celsius and stop when the temperature decreased below 36 celsius. I am simulating in LTSpice. ...
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127 views

Miscalculation of current for a pure inductive circuit in LTspice

A 10mH inductor is coupled to a 10V 60Hz AC supply as in the below circuit: Solution of the current amplitude for this pure inductive circuit is given as: But when I simulate this circuit in ...
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123 views
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Using Spice/PSpice (Vishay optocoupler) models in LTSpice

I am trying to use the Vishay-provided spice models of the 6N137 high-speed optocoupler in LTSpice. (Source: http://www.vishay.com/optocouplers/list/product-84732/) Both the "PSpice" model and the ...
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53 views

Why Does LTSpice Always Show Negative Voltages in a Rectifier Circuit?

Rather new to electronics, I'm trying to design some of my first circuits. One of them includes a bridge rectifier feeding into an opamp used as a comparator. However, I'm a bit perplexed as to why ...
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38 views

high frequency noise from multiple feedback op amp

I've built a multiple-feedback low-pass filter with a TL084IN op amp. I've simulated the filter for the chosen R and C values using LTSpice and it looks like I was expecting: . I've also assembled ...
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24 views

How to generate PWM signal with low voltages using Schmitt trigger or linear circuits

I want to design PWL signal to drive this Mosfet so i need to generate PWL signal using Schmitt trigger circuit or using any oscillator. I have an idea about Schmitt trigger but as i implement in LT ...
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47 views

How to enter .subckt model in Ltspice?

This is a LTSpice model I created for a single electron transistor macro model: ...
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62 views

LTSpice divergence between AC analysis and transient analysis for low frequency gain

A simulation is done in LTSpice (version 4.23k) There is an inverter: Fig.1: schematic 1mV small-signal input. AC analysis is run. Low frequency gain (Vout/Vin) is 20.69 dB (10.82 times). ...
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81 views

Using a single phase induction motor equivalent circuit in LTspice

I was planning to simulate a circuit which will control a single phase induction motor in LTspice where mains is 230VAC 50Hz. In my previous question, I failed to find an example: Modelling a ...
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36 views

Modelling a “single-phase permanent split-capacitor motor” in LTspice

I'm planning to use an AC fan in an LTspice simulation. The AC fan is made up of a single-phase permanent split-capacitor (PSC) motor. Here is the actual fan: ...
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54 views

Why this high-pass filter behaves like a low-pass filter for high frequencies, on this ideal LTSpice simulation?

I am simulating the usual active, first-order high-pass filter on LTSpice, as below: The Op-Amp I'm using is the following: This is the simulation result: What is the explanation for the ...
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32 views

How do I simulate a latching relays in LT spice

Here is my requirement. I have a dual coil latching relay. I am giving a pulse voltage to one coil to close the contact and stay contact until second coil is energized with another pulse. Is there a ...
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56 views

Why Doesn't SPICE Show the Discharging of a Capacitor after Input Voltage is Removed

I have a very simple circuit that includes a capacitor meant to provide a few seconds of battery-like backup to a few LEDs when power is removed. In real life, it does exactly that. However, when I ...
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35 views

Narrow bandpass filter using maximally flat LPF prototype design

I'm doing a project involving wireless power transfer, where an LED will be turned on via 2 induction coils (tx and rx). The interfacing power circuitry for this has already been figured out (an ...
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39 views

LTSpice constraints on plots

A have a circuit for which I have parameterized some of its resistors with the .STEP command. Consequently, I have many different graphs when I simulate the circuit. I would like to know if it was ...
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1answer
29 views

What is the syntax for modelling a non-linear element in Spice?

Suppose I have the following circuit. My question is how do I write the net-list in LTSpice such that f(i) = i^2 + 2 (for example) ? I couldn't find the syntax on the internet.
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26 views

Simple Interconnect circuit to simulate crosstalk in ltspice

I want to implement a very simple interconnect circuit to simulate crosstalk in ltspice because I am new to this area of crosstalk. Where can I find such a design? I have searched in the net but all ...
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122 views

How can I implement a solid state relay in LTSpice?

I want a specified DC input voltage or above input voltage of a solid state relay to activate it. I want 3V or above DC input to turn on the relay's output switch. Here is the simple diagram: Is ...
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2answers
105 views

How do I simulate a dc-dc boost converter in LTspice?

For a electric circuits lab I had to implement a dc-dc boost converter circuit and take certain measurements while I varied the duty cycle of the pulse applied to the MOSFET so that I could observe ...
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31 views

Why LTspice is showing singular matrix error in the following inverter circuit?

While simulating this circuit I am getting an error of singular matrix. Any advice?
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31 views

bjt current biased in ltspice

For some reason when current biasing a very simple BJT common emitter circuit in ltspice, the current source needs to produce a massive amount of voltage. Why would this be? I'm biasing it at a Q ...
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57 views

LTSpice output looks very odd when I use LM7805

LM7805 output is supposed to be 5V but it's very irregular and it's close to zero. I also tried adding a series resistor to the power supply but it was no use. Also, it takes forever to complete the ...
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136 views

How can I link a component's current to variable resistor value in LTSPice?

In LTSpice I want to implement an LDR resistor which changes due to the current passing through an LED. I want the current through the LED (D1) to vary LDR. I want to use the LED's current in an ...
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77 views

Is there a potentiometer model for LTspice?

I started designing a model for a three-terminal potentiometer in LTspice, since none are included and it's such a common component. Drawing the .asy symbol and the wiper terminal, it dawned on me ...
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64 views

add transistor model to LTspice

I'm trying to add the mmbt3904lt1g model to LTspice. - I've copied its data from the MMBT3904LT1.LIB.txt in the standard.bjt library. - I've added an NPN to my schematic then I've changed its value to ...
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64 views

LTSpice D flip-flop not working

I'm an absolute beginner with LTSpice; my first test circuit uses a few D flip-flops: four of them as clock dividers (to divide the clock frequency by 16), and then 3 as delay blocks (to delay the ...
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18 views

Relabeling pin names of a model without replacing pin names

After downloading a model with pins only labeled as what seems to be hexadecimal numbers. I want to relabel the pin names. As the pin names contain integers, "find and replace" all pin appearances ...
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88 views

How to change the temperature of sub-circuits in LTSPICE

I have subcircuits of a solar cell (resistors and diodes) in LTSPICE. I want to connect the solar cells (sub-circuits) together. However, each solar cell has a different temperature. I can set the ...
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79 views

How to simulate a real inverter?

I'm new to digital electronics and I want to simulate in ltspice a circuit which contains a couple of 74LS04 inverters. What represents the "Test conditions" under the switching characteristics in the ...
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30 views

Half Wave Voltage Doubler Simulation stuck

I'm trying to simulate the following circuit on LTSpice simulate this circuit – Schematic created using CircuitLab The capacitors have 10Meg Parallel ...
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58 views

LTspice IV ir2110 H-bridge simulation wierd behaviour

I want to simulate H-bridge using LTspice. At some point Ho stops working correctly. I am using ir2110 typical connection as schematic. This si up to the point where is it working ( but schematic not ...
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57 views

Demonstrating back EMF on an inductor in LTSpice

I'm trying to demonstrate back EMF on an inductor in LTSPice with this model: https://dl.dropboxusercontent.com/u/16979265/Draft2.asc I'm expecting the voltage on the inductor to have a negative ...
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96 views

What does a circuit's frequency response in dB refer to?

This is a simulated AC analysis of a small noise generating circuit. and comes from this circuit I have one of those fundamental but embarrassing beginners questions. What does the solid curve ...
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82 views

Input/output impedance of microcontroller

how to calculate the input and out put impedance for a micro controller , for the purpose of modeling in LT spice , for example RX610 family from Renesas For example the lumped characteristics can ...
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50 views

Why a DC coupled sine input signal will make my biased emitter follower looks like unbiased in LTspice?

I'm trying to simulate a biased emitter follower in LTspice. The dc operating point seems to be wrong once I used a DC coupled sine input signal(zero offset, 5V amplitude, 60Hz), it is almost 0V at ...
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4answers
78 views

High Pass filter gain at higher frequency than cutoff frequency

As i know , it's very common easy to find cutoff frequency and calculate gain at highpass filter. This is my circuit; simulate this circuit – Schematic created using CircuitLab My ...
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1answer
158 views

How to model a noisy Zener diode in LTSPICE?

I'm trying to simulate a white noise generator of the Zener diode style. I'm going with current amplification, rather than the more traditional voltage amplification just because. My problem is that ...
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45 views

Issues with LTSpice Sallen-Key single-supply Simulation

I'm having trouble with simulating a Sallen-Key single-supply low pass filter using LTSpice. After fiddling around with the circuit for an hour I'm hoping for some assistance in troubleshooting. For ...
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24 views

Adafruit Anemometer

Recently I bought an anemometer from Adafruit. I was wondering is there is any way or approach which I can simulate the sensor for measuring the wind speed. If there is any software able to simulate ...
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72 views

Without C3 this Colpitts oscillator won't oscillate - why?

The pictured Colpitts oscillator circuit will not oscillate on a plug-in protoboard without C3 and its connection to ground in place. In LTSpice the circuit oscillates with or without C3 and its ...
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51 views

Are voltage transients on LTspice simulations significant?

I (incorrectly*) modeled this simple answer in LTspice IV and am seeing seemingly random instantenous voltage spikes up to +/-1kV on the output of the depletion nMOSFET. Are these real? If so, are ...
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1answer
45 views

LTSpice parametric subcircuit instances

I want to compare signals from my fancy subcircuit (very complex) and multiple subcircuits level1 (should be almost equivalent, ...
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15 views

Spice mosfet, user selectable parameters ires, cox, pox, vtn from a 3rd party model

I have a spice model for the part ald1103 from advanced linear devices that contains parameters to be filled in by the user, presumably to support custom ASICs using transistors from this ...
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2answers
59 views

Strange results for NMOS component in LTSpice

I am testing the I V curve of the mosfet in LTSpice I get strange results when the standard 'NMOS' componant is reverse biased, (when the source is more positive than the drain) I get tera-amps ...
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28 views

Is it possible to create a signal in LTSpice by using a stored data?

I have lots of sampled voltage signals data where I can plot them in MATLAB or write them to a text file for each sample. I would like to use these samples to generate input signals in LTSpice ...
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51 views

Plotting more than one voltage in LTSpice

I have a Spice netlist as follows. In this netlist, I want to plot V(3) and V(2) at the same time to the same plot pane. Writing only .plot v(3) or .plot v(2) can plot the corresponding voltages ...
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44 views

LTSPICE - Scale dimensions

I want to specify the scaling factors for my mosfet dimensions. How do I do it ? I am following some beginner tutorials but they have done everything in HSPICE. I use LTSPICE. And LTSPICE doesnt seem ...
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65 views

LTSPICE - Plot power

How do I plot power in LTSPICE ? I browsed a few tutorials. Acc to them, you click and ALT on the element you want to find power of. But my problem is I do not have a schematic. I prefer to build ...