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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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
60 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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29 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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26 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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52 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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2answers
134 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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4answers
52 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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41 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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2answers
47 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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17 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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1answer
76 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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1answer
72 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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27 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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42 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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27 views

I'm given Vpp, what is the amplitude (LTSpice)

Alright I can't seem to find an answer for this question. I'm given a Vpp (peak to peak voltage), what will the amplitude be in LTSpice? To be more specific, what I'm trying to do is simulate an ...
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2answers
51 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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3answers
83 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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3answers
80 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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3answers
48 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
70 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
109 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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2answers
37 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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1answer
64 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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1answer
47 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
30 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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13 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
56 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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27 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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47 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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1answer
36 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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2answers
57 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 ...
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84 views

Why am I having totally different outputs with the identical input signals of two different sources? [closed]

The question is about the above Schmitt trigger indented to convert AC signals to pulses. As seen, I use V2 as input in the simulation. The circuit above works both in LTspice and breadboard when I ...
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105 views

Correct way to simulate and visualize 230V AC voltage in LTSpice IV

I want to simulate a 230V ac power supply in LTSpice IV. Apparently LTSpice requires to input the voltage amplitude in some special format - e.g. for 230V you have to input 325 as amplitude (at least ...
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3answers
134 views

LTSpice power supply simulation: what is wrong with it?

I have simulated the LM723 based regulator circuit in LTSpice And after running it I got 16A currents (blue/green) on diodes in rectifier. The max current I supposed to get here was 3.3A. Please ...
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1answer
72 views

Unexpected LTSPICE Output - Voltage Mode Buck Convertor

I'm trying to simulate in LTSPICE a simple buck convertor taking 34V -> 20V @ 2.5A and I'm not seeing what I expect. Here is my circuit and some waveforms: The top half of the circuit is the ...
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1answer
46 views

LTspice: Is there any way to access .measure results from within a subcircuit?

I have a subcircuit in my LTspice schematic. It appears as a schematic block. Within the subcircuit's schematic there is a .MEASURE statement. How can I view the results of this .MEASURE statement ...
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32 views

Parameter step/table in LT spice

I am simulating somewhat complex behavioral sources in LTspice - and am having difficulty getting a set of parameters to be accepted. See schematic below of a bidirectional buck/boost converter. I ...
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2answers
58 views

How signficant is leakage inductance in a flyback converter?

In designing some flyback DC-DC converters (to give us isolation), we have been simulating potential designs in LTSpice, which has gone well. (Isn't LT great at documentation? Pretty much perfect ...
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1answer
53 views

LTSPICE Bridge Rectifier - Odd Output

I'm trying to simulate a simple full wave rectifier in LTSPICE. The output I am getting is not what I am expecting. In the picture below, the green line is the voltage output from the + terminal of ...
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1answer
70 views

Simulation of TDR using LTSpice

I'm trying to simulate a TDR based on the figure below, and one of the scenarios is a short circuit. The simulation should last for 140ns. The parameters are \$Z_A = 50 \Omega \$ \$T_A = ...
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89 views

Importing a verilog-a compact model in ltspice

I have a Verilog-A compact model, and would like to import it in LTSpice. I tried to google this, but to no avail unfortunately. Can anyone tell me how to do this if possible? By the way, in spectre ...
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3answers
62 views

Where do I find models for various common op amps for use in LTSpice

I have just started using LTSpice. I need to simulate a circuit with op amps, where the parasitic elements of the op amp may effect performance. So I need to try different 'real' op amps to see which ...
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1answer
122 views

Using crystal in LTspice (where to get values for RCL)?

I'd like to simulate a schematic in LTspice driven by a crystal. An capacitor representing the crytal (as a resonant circuit) however it needs some specific values. Is there a table of common values ...
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2answers
186 views

A question about negative dB in LTspice

Above is a screen-shot from an LTSpice simulation. It is a freq. response of an LC tank circuit with a 5V sinusoidal AC source. When I plot it, the y-axis is in dB. When I look at the voltage it ...
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2answers
121 views

Newbie question - sawtooth signal generation - capacitor discharge via bjt

I'm trying to realize a sawtooth wave generator. The circuit is composed by an op-amp integrator which creates the ramp. Then the integrator output is chained to a comparator with a fixed threshold, ...
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106 views

Cannot find SPICE models of audio transistors for LTSpice?

I need to simulate a circuit with the following transistors: MPS8050 OR MPS6560 AND MPS8550 OR MPS6562 But I cannot find any for LTSpice. http://ltwiki.org/ also doesn't have. TINA has these ...
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133 views

LTSpice Third Part MOSFET Model Won't Work

I am attempting to incorporate this mosfet model into ltspice: Part Page Model However nothing I do seems to work. I've placed the library both next to the main .asc, and in the ltspice /lib/sub ...
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1answer
82 views

Ltspice Transformer Simulation

I am trying to simulate a transformer with a turn ratio of 1:1. The voltage of the primary and secondary are equal but I am getting a different current in the winding (why?). Also I see some DC ...
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1answer
70 views

How to add a multi-emitter BJT to LTSpice?

I want to simulate the standard TTL NAND gate which contains a multi-emitter BJT transistor in LTSpice. I've searched the components available in LTSpice but didn't found this component. How can I add ...