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.

learn more… | top users | synonyms

0
votes
1answer
30 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 ...
0
votes
1answer
38 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 = ...
0
votes
0answers
11 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 ...
0
votes
3answers
38 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 ...
3
votes
0answers
40 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 ...
3
votes
2answers
151 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 ...
1
vote
2answers
72 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, ...
0
votes
2answers
53 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 ...
1
vote
2answers
56 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 ...
2
votes
1answer
52 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 ...
3
votes
1answer
46 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 ...
1
vote
1answer
15 views

LTSpice .STEP trace colours

When I use the .STEP directive in LTSpice to produce a range of plots using different component values, sometimes it displays each step in a different colour and other times it doesn't. What is the ...
0
votes
1answer
39 views

LTSpice Instrumentation amplifier simulation output

I am using an LTSpice model for an instrumentation amplifier (AD8222) to learn how to simulate things in LTSpice. My output is not what I expected. My model is based on this description: ...
2
votes
1answer
45 views

LTSpice SEPIC design low freq ringing

Further to the SEPIC design I asked about in LTSpice SEPIC simulation current spikes, I have a new problem. The output voltage is OK and the inductor current waveform looks much better but the ...
0
votes
1answer
58 views

LTSpice SEPIC simulation current spikes

I am designing a SEPIC power supply using the LT3758. I have simulated the circuit in LTSpice and all the waveforms are as expected except the L1 current. Here I see massive overshoots when the MOSFET ...
0
votes
0answers
18 views

CCVS description in LTSpice netlist

I have been learning netlist recently and I have got a problem with the dependent source especially CCVS and CCCS. This is my source code. When I run this code I get an error which ...
0
votes
1answer
31 views

LTSpice Full Wave Controlled Rectifier Erronous SCR Breakover

I'm attempting to simulate a full wave SCR rectifier: However it is not behaving correctly. In my setup V3 controls one pair of SCRs, and V4 controls the other. All the math on the side is just for ...
0
votes
2answers
61 views

How are conflicts between voltage sources or signals resolved?

I am trying to understand what happens when 2 supplies or voltage signals are tied to together as I come across similar situations where a Totem-pole output is also being pulled-up by a weak pull-up. ...
1
vote
0answers
41 views

Resonant circuit using LTSpice

I'm a college student and I was supposed to draw the Bode-plot of the following resonant circuit. I obtained this. My questions are: shouldn't I have obtained a bell-shaped curve? How can I find ...
0
votes
2answers
100 views

LTSpice Simulation Showing Inaccurate Results and Excessive Current

So I'm trying to make the following simulation work properly to verify some hand solving for a circuit. The circuit is an LC tank with some diode clamping, and an initial capacitor voltage of -50V. ...
0
votes
0answers
28 views

Measure Input Z of Tranformer with LTSpice

I would like to more accurately model audio frequency transformers in LTSpice. To that end I tried to verify the input impedance using a model like the following: This is supposed to model a ...
1
vote
1answer
59 views

Measuring Input Impedance of Transistor with LTSpice

How do you measure the input impedance of a transistor with LTSpice? Consider the following circuit: The above just biases a transistor so that the collector is 1/2 the supply. I used a current ...
0
votes
1answer
36 views

LTspice `Icrating` of BJTs

I see LTspice has an Icrating parameter for BJTs. As far as I can tell this isn't part of SGP (SPICE Gummel-Poon model) and also not present in other flavors of ...
0
votes
3answers
62 views

How to model a DC motor in LTSpice if only its nominal voltage and max. current is known?

Is there a simple way to model a DC motor in LTSpice when controlling it with a PWM signal? Lets say the motor is 9V/2A. I was thinking the safest way to measure the stall current and use the nominal ...
3
votes
1answer
338 views

Why am I getting negative base current in LTSpice simulation?

When I was trying to bias an NPN transistor I noticed that the base current Ib is negative in LTSpice. So for the sake of simplicity I only apply voltage to the base-emitter junction. As you see in ...
0
votes
2answers
61 views

Automatic parameter search for a given output in LTSpice

I am simulating a circuit on LTSpice and was wondering if there is a way to set output parameters for LT to aim for by adjusting values of other components. I have used some software in the past that ...
6
votes
1answer
319 views

How to plot “voltage drop” across a specific component in LTSpice?

In the above circuit I can only be able to plot |Vr1+Vc1| = V1 in green plot and Vc1 in blue plot. I use the voltage probe in LTSpice and click on the lines to obtain the plots. If I click on the ...
0
votes
2answers
144 views

Simulation shows my op Amp has a gain for infinite frequency spectrum

I (could not) have designed an Op Amp and made the AC simulation on LtSpice and I saw something annoys me as below: and here is the schematic, a pretty basic op amp structure: As you see, at ...
0
votes
0answers
56 views

Adding a component to LTSPICE problem

I'm having trouble adding a zener diode to LTSPICE. I found the following codes for the 1N4735A zener: ...
0
votes
1answer
69 views

Sine to pulse converter circuit help

I have a sine to pulse converter box(LM2903 is used), it works very well and I also have the circuit schematics. The converter converts the mV level sinusoidal signals to pulses. I want to rebuild ...
3
votes
3answers
92 views

Phase margin analysis of a [diy] PMOS LDO [with LTspice]

I'm somewhat familiar with using LTspice to do phase margin analysis for a classic i.e. obvious negative feedback path opamp circuit; in fact I've done that analysis successfully for fixing real opamp ...
0
votes
0answers
62 views

How to measure the rolloff/corner/cutoff frequency in LTspice with a MEAS statement?

In hspice you can do .MEAS AC corner when VDB(out) = -3 to get the -3dB rolloff frequency. This syntax doesn't work in LTspice (I suspect because VDB is not ...
-1
votes
2answers
109 views

Why isn't this inverting amplifier using a LM741 op amp clipping at the power supply voltage?

I built an op amp on a breadboard, and in LTSpice, and in both cases the peak output (Vpp-out) is ~8.2V with a power supply ±5V. Here's an image of my LTSpice schematic: I was testing out ...
0
votes
2answers
128 views

LTSPICE - How to create PWM with rise time

A simple PWM circuit is simple to create using LTSPICE, such as: ...
1
vote
0answers
47 views

Using SPICE to model dV/dt filter for inverter motor drives

I am starting to learn LTSPICE to create model where I can test various passive filter topologies for inverter drives where the output PWM has very short rise times and high switching frequency. I ...
2
votes
1answer
45 views

Setting manual thermal voltage for a diode in LTSPICE

I want to simulate some series and parallel connected solar cells with the same reference temperature but different operation temperature for each cell. To do so, I need to configure the thermal ...
1
vote
2answers
62 views

how to find specific component with ltspice?

I'm having trouble every time I need to find a component with Ltspice. Normally I manage to find what I need but not for the current component. I need a 2n2222 transistor. I've tried to enter words ...
1
vote
2answers
58 views

Transformers and Electric power Ltspice

i was looking for the Energy conversion efficiency of my circuit in Ltspice, but i find out that my Transformers is giving me strange power values i mean with K = 1 the P1 should be equel to P2 but in ...
3
votes
1answer
51 views

Buck converter simulation

I am having some troubles to simulate a Buck converter in LTSpice. I added a picture of my schematic in which a use an IGBT (IRGP20B120U-EP from International Rectifier) and a fast recovery diode ...
0
votes
2answers
91 views

SPICE modelling of microwave cavities using a circuit

Hi I am new to SPICE and after doing some research into the spice software, I need some help understanding which type and how to model microwave cavities in SPICE. I want to model a microwave cavity ...
1
vote
1answer
70 views

how to position precisely the cursor in a bode diagram with LtSpice?

I'm using Ltspice, and when I have a bode diagram, I have a cursor. I'm able to move the cursor over whatever value I'm using. However, sometime I need a precise frequency. When I try to enter it in ...
0
votes
0answers
49 views

Adding noise source to the Input

I have a working model on LTSpice where the input is a pulsating one. Can someone guide me how to add a noise source to the input ?(the results are obtained in eye diagram format)
2
votes
1answer
80 views

Circuit simulation shows gain with only passive components. Why?

This feels like an ignorant question, but here it goes. I'm trying to understand the antenna circuit from the 430 MHz reference design for TI's CC1125 transceiver IC. The antenna circuit is at the ...
1
vote
0answers
47 views

Add a trace from a directive in LTSpice

I have a circuit in LTSpice in which I want to measure some differential voltages, currently I'm manually adding the traces using the "Add Trace" menu in the plot view and writing its expressions. I ...
1
vote
0answers
38 views

What is wrong with this LTspiceIV model of a Deliyannis bandpass filter

I'm trying to analyze a Deliyannis bandpass filter at fc=7.15Mhz. I have constructed the following in LTspiceIV: which results in the following net list: ...
0
votes
0answers
27 views

Time dependent parameter LTSPICE

I would like to ramp up the duty cycle to a certain point and then hold it at that specific level. The duty cycle needs to be set through the Ton of the Pulse generator that is used for the pulses. ...
0
votes
1answer
49 views

Problem with automating LTSpice

I'm trying to automate LTSpice using the command line. I have tried the following command several times: test.asc -run -b However, it only opens my schematic in LTSpice and does not run it! I have ...
0
votes
1answer
35 views

.step function LTSPICE in multiple panes

I am trying to simulate multiple different frequencies of a buck converter. I know how to step the parameters, but I would like the graphs in separate plot panes. Any clue on how to do that? Two ...
0
votes
0answers
46 views

IGBT switching losses

I was wondering if somebody has experience in simulating the switching losses of IGBTs and MOSFETs in LTSpice. I would like to make my own IGBT models, based on the parameters given in the datasheet. ...
1
vote
2answers
112 views

Spikes, surges and noise sources in LTSpice

I am attempting to simulate a DC-DC power supply in LTSpice (using LT3748, 48V in, 5V 3A out). There is concern about the amount of noise that will be on the 48V input rail, and so we want to ...