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Questions tagged [falstad]

An online, open-source circuit simulator

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strange coil effect in Falstad

I was just using Falstad to create a circuit and while I was trying something I noticed this. When I close and open the switch back to back it was supposed to create a curve. But turns out it's only ...
kaan's user avatar
  • 377
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2 answers
58 views

Falstad Circuit Simulator: Issues Simulating a Peak Detector [closed]

I was attempting to simulate a peak detector circuit and noticed that when the input to the peak detector is a square wave, the simulator goes a little nuts and the voltage across the capacitor ends ...
user24331180's user avatar
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1 answer
33 views

Buck converter Sim not working

I am having some issues getting a simulation of a buck converter I've been trying to design to work. For some reason the op amp (circled in Red) isn't seeing any voltage on either of its inputs (both ...
Bren's user avatar
  • 45
1 vote
1 answer
56 views

Reusing an output in Falstad

I'm simulating a logic circuit in Falstad and a particular output X is used multiple times in the circuit. Can I take input as X without drawing many wires from X?
Shub's user avatar
  • 129
1 vote
1 answer
97 views

Why isn't this circuit working in Falstad as expected?

While trying to simulate a simple circuit using a N-Channel MOSFET, I encountered a problem. while supplying 3.3V to the GATE pin, I would expect a way higher current to flow, more like 7A. But ...
Fazeli24's user avatar
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Current/Voltage phase shift issue with low/high capacitor capacitance

How to make voltage/current 90 degree phase shift properly? In my PWM->sine "converter" the current/voltage phase is shifted 90 degree only with low value capacitor (10 uF), but no shift ...
Vadim Ostanin's user avatar
1 vote
1 answer
152 views

Anyone have a Falstad simulation of a two transistor common-emitter amplifier? [closed]

I am trying to understand more fully how transistor amplifiers work and I've found the Falstad simulations to be very informative, especially the ability to place a mouse at any point and look at the ...
rhody's user avatar
  • 308
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1 answer
162 views

Falstad Circuit - Why is the current still flowing through the transistors?

I'm trying to simulate a simple signal amplifying circuit using three transistors as shown below: (Note that the LED isn't turned on) But when I open the switch, the current still flows normally from ...
Nihilo's user avatar
  • 3
3 votes
1 answer
313 views

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
  • 33
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0 answers
77 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
141 views

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
  • 105
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1 answer
113 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
  • 129
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0 answers
69 views

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
153 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
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1 answer
123 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
73 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
116 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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0 votes
3 answers
355 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
189 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
395 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
240 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
4k 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
334 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
  • 107
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
727 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
  • 287
3 votes
2 answers
976 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
3 votes
0 answers
1k 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
763 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
0 votes
1 answer
75 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
330 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
1 vote
1 answer
373 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
486 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
  • 163
1 vote
1 answer
205 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
125 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 ...
learningtech's user avatar
3 votes
2 answers
3k 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
  • 515
0 votes
1 answer
2k views

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
3k 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
  • 176
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
15k 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