# 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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### How do you simulate voltage noise with LTSpice?

Is there a way to setup a voltage supply with voltage jitter/noise? I want to experiment with filtering out noise on various voltages etc. but not sure how to configure LTSpice to create a noisy ...
38k views

### LTspice: Vary a resistor's value over time

I want to simulate the load regulation of a power-supply. I'm sure I remember being able to vary the value of a resistor over the course of a simulation in LTspice, but I can't remember how. Anyone?
3k views

### Why doesn't LTSpice predict this op-amp oscillation?

I'm developing a circuit to act as an electronic load for bench testing power supplies. An earlier question about how to test this circuit received several very useful answers and can be found here: ...
15k views

### Why is my simple boost converter giving me such a high peak output voltage?

I am trying to understand switch-mode power supply fundamentals through a simulation in LTSpice. I wanted to build an excruciatingly simple boost converter circuit following a teaching model often ...
2k views

### LTspice sinusoidal voltage source with offset much larger than amplitude broken?

I've been troubleshooting an analog circuit and have just come to the realization that Sine Voltage sources at mV are broken. Here is one that is supposed to provide a 1mV 1Hz sine wave on top of a ...
17k views

### LTSpice Automation

I have a battery-powered boost converter and I'm attempting to measure the maximum input (battery) voltage droop under various load conditions of high current draws (different duty-cycles/...
8k 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 line ...
24k views

### Why does LTSpice say that my “Matrix is singular” for this ideal-transformer circuit?

I'm trying to do find the voltage over R1 in the following circuit, where L1/L2 is an ideal transformer. LTSpice complains that the "Matrix is singular". Why? I've tried to play around with lots of ...
10k views

### How to view and customize beta of a transistor in LTspice

If I need to set beta to a custom value, is it possible to make a customized transistor with a beta of my choice? In other words, can I edit a ready or generic transistor's beta and save it as a ...
25k views

3k views

### LTSpice: How to vary resistances in a simulation depending on the value of a voltage?

I am trying to implement the Hodgkin-Huxley model for simulating neurons using LTSpice. One feature of this model is that the resistances at any given time actually depend on the transmembrane voltage ...
11k views

### LTSpice (mac) How can I display the current in the schematic?

I want to simulate a circuit and display the current directly in the schematic. However I am only able to display the voltage. Here you can see an example where someone actually displayed the current ...
7k views

### SPDT in LTspice

I'm currently new to using LTspice as a circuit simulation software. Right now I'm trying to check if the IC (BD6221F-E2) that I included in the program is working. The process of making this IC is ...
2k views

### Why does the LTspice op amp stability tutorial recommend open loop analysis?

I have performed a hand analysis on an amplifier circuit that I am suspicious of, and I am still suspicious, so I want to validate my hand analysis with LTspice. I found this tutorial online: http://...
4k 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 ...
5k views

### DC power supply simulation trouble

I'm trying to simulate a relatively simple AC->DC power supply in LTSpice, but it's not quite cooperating with me. I've followed this schematic: only replacing potentiometers with resistors due to my ...
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### LTSpice: Can I vary schematic temperature over time?

I'm trying to simulate a temperature sensing schematic with a latching function (meaning that the schematic should go to overtemperature mode at let's say 75C and go back to normal at 50). I can do a ...
17k views

### “Unknown subcircuit” in LTSpiceXVII

I'm attempting to simulate a circuit that is intended to take a 5V/GND input and make split +/- 2.5V rails with a virtual ground. When I try to simulate, LTSpice complains about "unknown subcircuit" ...
7k views

I am very new to LTspice. I would like to ask "How can I add a photodiode in the Ltspice?" Is ideal photodiode (or any specific) model already included in the LTspice or do I need to create third ...
498 views

### How to break components in SPICE?

I've been learning SPICE over the past few days, using the LTSPICE program. One thing that just escapes me, is how exactly do we know when a component's absolute maximum ratings have been exceeded? ...