Questions tagged [falstad]

An online, open-source circuit simulator

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Unable to get my astable multi-vibrator working in LTspice

I'm trying to build a basic square wave oscillator using an astable vibrator made with an op-amp for my Intro to Circuits class. Unfortunately, I cannot get LTspice to simulate the oscillations. I've ...
Jgely's user avatar
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34 views

Circuit simulation of PWM has a rapid loss of voltage in Falstad

I made a PMW in falstad that works only for a few seconds bevor the voltage in whole circuit drops to zero. I already tried to redirect the diodes with no effect. https://www.falstad.com/circuit/...
P. W.'s user avatar
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3 answers
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What is the origin of negative offset in this amplifier circuit?

I'm working on a class AB power amplifier for a school project. The desired specifications are a load impedance of 4-16 Ohms, 1% Total Harmonic Distortion (THD), and 10W amplification. The input ...
T1P0Z's user avatar
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1 answer
63 views

Phase shift in clamper circuit

I'm trying to simulate this clamper circuit in falstad: But there's a phase shift in the output voltage of my circuit. Is this expected? Am I doing something wrong? Can someone please explain? (I'm ...
Shub's user avatar
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Avalanche effect of a Zener diode, or simulator bug?

On the Falstad simulator, I tried to illustrate the phenomenon of the avalanche effect of Zener diodes. I've added a capacitor to remove the DC component, too. However, I'm not sure that the (very low)...
Aramya's user avatar
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1 vote
1 answer
73 views

Falstad Schmitt trigger problem

In the given problem, I know that the answer should be (d), because it should act like a Schmitt trigger. But when I try to model this circuit in Flastad, I suddenly get that the answer (b) is right. ...
KrtekUser's user avatar
0 votes
1 answer
75 views

555 IC 1 minute delay timer not working in simulator

I have a problem in Falstad that when making a 555 IC based signal delayer that should delay a power-off of a certain device, that the whole circuit behaves really weird and doesn't work as stated by ...
Marek Bílý's user avatar
2 votes
1 answer
69 views

Finding Ve for a 3 input AND gate TTL circuit for different logic combinations

I'm designing a circuit that takes 3 24V input signals and pulls a 50 ohm resistor to ground when all three signals are high. My main concern is the voltages across different pins of the transistors ...
Callum Rafferty's user avatar
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1 answer
78 views

How do I make a good frequency multiplier for a basic sound chip? It uses a DAC, so it needs a high input frequency for lower output frequency

I'm building a simple triangle-wave sound chip based around a 4-bit DAC. It works, but I have to have each individual square wave for each of the 16 notes (which are bass-range, 60Hz-238Hz.) I want to ...
cheese's user avatar
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2 answers
185 views

High-current transients with LM317 LD driver in Falstad

I have been building a laser diode driver in Falstad, but for the first 200 μs there is a current spike of over 70 A! This would mean instant death for my laser diode. If you are curious the laser ...
cats are the best's user avatar
2 votes
0 answers
109 views

Is there a way to approximate an optotriac in CircuitJS / Falstad?

Falstad does not have an optotriac part. I've opened a feature request issue on the CircuitJS GitHub to ask for one to be added, but is there a reasonable way to emulate an optotriac given the ...
Polynomial's user avatar
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-2 votes
1 answer
242 views

Turn an LED on/off LED with a flip-flop counter [closed]

I want to make a 7x7 LED matrix which begins to turn on the first one LED to the last and then turns off the way back (spiral matrix.) I'm trying to turn the LEDs on/off by using signal created by ...
Tri Nguyen Minh's user avatar
1 vote
0 answers
204 views

Falstad, Micro-Cap, LTspice

I've just started with Electronics and am enjoying the Falstad simulator for seeing how components work, current flows, etc; really great. I've become aware of Micro-Cap and was aware of LTspice as, ...
Allinthemind's user avatar
1 vote
2 answers
2k views

Falstad Circuit not running

I created this Falstad circuit that is supposed to run to toggle between the 3 circuits to power the LED. The top AND gate leads to a circuit that makes a strobe light effect. The second is supposed ...
sebas pineda's user avatar
-1 votes
3 answers
255 views

simulation (in Falstad's app) of thyristor using transistors fails

I am trying to simulate thyristor behavior with transistors PNP and NPN but it fails (is it a bug of app?). When lower switch is open(and was never closed) and upper closed then current flows through &...
quester's user avatar
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2 votes
1 answer
1k views

How to simulate external voltage source in Falstad?

I am looking to simulate circuits on Falstad: http://www.falstad.com/circuit/circuitjs.html . One of the features on the website is the ability to add an external voltage source programmable with ...
Steven Underhill's user avatar
1 vote
1 answer
542 views

DC current through capacitor in Falstad

I am using the Falstad simulator. I do not understand why am I getting a DC current through a capacitor in simulation. This must be an error from the simulator. Please, let me know if I am sane, I ...
JCSB's user avatar
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3 votes
2 answers
817 views

Is this component in falstad a tl431

I'm self studying electronics, I am now familiarizing myself with the tl431, which is pretty much a "variable zener" aparently. I was shown the following symbol. I would like to simulate ...
Joaquin Brandan's user avatar
2 votes
1 answer
977 views

Hold-on-hold-off soft latch power switch circuit

I'm trying to make a "hold-on-hold-off" type soft latch switch circuit, but I'm having a little trouble. I've found tons of "press-on-hold-off" types, but I haven't been able to ...
MyFingerHertz's user avatar
-3 votes
2 answers
639 views

Falstad - a bug with mosfets?

I have a schematic in Falstad. It is almost symmetrical (the mosfets are connected by drains and "SWAP D/S" is enable in the second mosfet to be able to connect both). And this symmetrical ...
Proboszcz's user avatar
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1 answer
73 views

I want to do make an and-gate but why do I get high when my swich is off?

I want to do make an and-gate but why do I get high when my swich is off?
Eleinor 's user avatar
0 votes
1 answer
266 views

"Noise" in simulator

I have been working on a simple circuit which performs XOR operation. The problem is that I am seeing a noise-like graph when both inputs are set to 1 (5V) and I have been doing a research on what it ...
Curious Student's user avatar
0 votes
1 answer
314 views

BJT differential amplifier with active load

I completed the theoretical parts of the DC and AC analysis. I want to test them with the simulator. Both DC and AC analysis failed. I killed DC sources in the AC analysis section and I short-...
Hasan Harman's user avatar
2 votes
2 answers
416 views

Falstads circuit simulator : capacitors have initial voltage?

I started playing with Paul Falstad's circuit simulator applet to see if it would be useful for my intro physics students. However, I'm running into a quirk regarding capacitors which I don't really ...
Semiclassical's user avatar
3 votes
1 answer
1k views

Circuit simulates in Falstad but not in LTspice

I'm having trouble simulating what should be a simple circuit in LTspice. I am designing a simple PWM-regulated power supply, but I'm running into problems when I try to simulate it. When I simulate ...
Jzuken's user avatar
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1 vote
1 answer
166 views

Diode letting voltage through in circuit simulator - bug or real?

I'm pretty new to electronics, and so I've been modelling my circuits in a Falstad's circuit simulator. I noticed something which I did not expect, and am curious - is this effect real, or is this a ...
AMADANON Inc.'s user avatar
0 votes
1 answer
122 views

Beginner - Why do voltage/current behave this way

I was checking falstad and came around this resistor circuit which lost me completely : Knowing that input voltage is 5v and current is 17mA : 1- Why is the voltage 0 after the 200Ohm resistor ...
Soufiane Touil's user avatar
2 votes
1 answer
1k views

Attempting an audio pre-amplifier circuit with falstad.com

I'm new to electronics and discovered the falstad.com simulator. I wanted to model this audio pre-amplifier circuit: So I went into falstad and drew this: My pre-amplifier circuit on falstad The ...
John's user avatar
  • 435
3 votes
2 answers
2k views

Piezo speaker equivalent for circuit simulator

I am using Falstad's circuit simulator to test a design of an Op-Amp based microphone-speaker system...kind of like a megaphone, but the speaker is going to be a piezo plate. Falstad does not have a ...
traisjames's user avatar
1 vote
1 answer
2k views

How to Plot X/Y in Java Circuit Simulator

Does anyone know how to select the Y variable when doing an X/Y Plot in Java Circuit Simulator? I tried many things and none have worked.
Takide's user avatar
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1 answer
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Kill Switch schematic

I want to make a kill-switch pedal with on/off LEDs for my guitar. I tested a simple schematic but every time I ground the circuit like the schematic i put below i get an error: voltage source/...
Segmentation's user avatar
2 votes
1 answer
2k views

How To Charge a Battery in Falstad Circuit?

I'd like to model the charging of a battery in Paul Falstad's Circuit simulator. But, i cannot find a battery component. Is there any way to do this? thx
johny why's user avatar
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1 vote
2 answers
2k views

Active Notch Filter Simulation

I need to build an Active twin- notch filter that will filter out 60Hz. I am following the schematic bellow: To test the schematic, I am simulating it on Falstad Circuit Simulator, but the 60Hz is ...
Liam F-A's user avatar
  • 198
0 votes
2 answers
115 views

OP Amp - Finding currents [closed]

I am having some difficulty figuring out V_out. I know that it is going to be inverted because V+ = 0 and I know that V- ≠ 0. I don't really know how to go about finding the currents in the system to ...
user3482104's user avatar
8 votes
4 answers
14k views

Is there a more realistic circuit simulator than Falstad's?

In real life, the 100mA load in the circuit below will experience a brief, partial loss in current and and a drop in voltage when the 4A load is engaged but this simulator is too basic to show that. I ...
Arewfawe Waefadffawe's user avatar
1 vote
2 answers
1k views

Why isn't this Elenco circuit working in Falstad's simulator?

I'm learning electronics engineering with the Elenco 130-in-1 kit, and I'm trying to get better at visualizing how these circuits are working by making them in the Falstad simulator, but the first one ...
Nathan Wailes's user avatar