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 a very liberal license, it is lightweight, and isn't crippled in any way.

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Why is my LTspice simulation so different from my calculation by hand?

This is the circuit: $$V_{in} g_{m1} + \frac{V_{in}} {r_{o1}} = (V_{in} - V_o) s C - \frac{V_o} {r_{o2}}$$ $$\Rightarrow \frac{V_o} {V_{in}} = \frac{s C - g_{m1} - 1/ r_{o1}} {s C + 1/r_{o2}}$$ The ...
kile's user avatar
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Coil current discharge on a resistor in a simple circuit

Attached is a picture with the circuit in LTspice. There is a 5 volt pulse voltage source. Parallel to the voltage source I connected a coil and a resistor. Why don't I see the high voltage on the ...
ניר ברוך's user avatar
1 vote
2 answers
119 views

No DC offset observed in the CE amplifier circuit part

The objective is to make an audio amplifier. We have decided to make one that has four stages: a pre-amp with a gain of around 120, the next one is a CE amplifier with a gain of around 5, the third ...
JackSparrow9875's user avatar
3 votes
1 answer
98 views

LTspice 24 `.ini` file location

Background LTspiceXVII had a well-defined location for its .ini file. LTspice17 (i.e. the successor to XVII) stores its .ini ...
pfabri's user avatar
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3 votes
1 answer
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Operational amplifier question in LTspice

I was asked to pick values for the resistors (I picked R2 = 78 Ω and R1 = 2 Ω) and for Vminus and Vplus. Can someone please explain what these voltage sources are for and what values I should give ...
Adi Goyte's user avatar
2 votes
0 answers
99 views

What is the point of analysis and biasing calculations when real world performance is going to be much lower in analog circuits? [closed]

I am making a 3-stage audio amplifier as a course project. The first stage is a differential amplifier, the second stage is a common-emitter amplifier, following that there is a passive filter and ...
Koustubh Jain's user avatar
0 votes
1 answer
61 views

Simulation time for Full bridge

This is a full bridge circuit which I am trying to simulate in Ltspice with a snubber. When I use ideal switches instead of MOSFETS, the simulation works fine. But when I use the real mosfet models, ...
Andr7's user avatar
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CML Latch simulation in LTSpice

I am trying to simulate a CML Latch in LTSpice (schematic below), but the simulation results do not seem right. I am using N_50n transistors from BSIM4 model. L = 60n for all transistors, W = 10u for ...
Kamal's user avatar
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2 votes
2 answers
169 views

Clipping of output waveforms in a push-pull amplifier circuit with op-amps, how to fix?

I don't know what the circuit is called; I found it in the suggested schematics of a Resolver to Digital Converter IC. The circuit is an amplifier circuit that has two push-pull amplifiers and a bunch ...
Srivatsen R's user avatar
1 vote
0 answers
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Transformer Model LTspice - Flyback Voltage Clamped on Primary but Still Present on Secondary Side

I'm simulating a circuit in LTspice using a pulse transformer to drive a JFET gate. The circuit is supposed to work as follows: We drive M1 (N channel FET) to pulse current from a 20V source through a ...
L30LVC's user avatar
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2 answers
482 views

LTspice: weird behavior of simple RC circuit

I try to model a simple RC circuit with input of 2 A DC and I get an out voltage (Vc) of 2 TV. I am not sure what I am doing wrong. EDIT: This is for MacOS
user510's user avatar
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Instrumentation amplifier using folded cascode op-amp is not working

I made the sizing for a folded cascode operational amplifier, which is working well, however when I am trying to implement an instrumentation amplifier in LTspice using the blocks, it does not amplify ...
tgarmp's user avatar
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4 votes
2 answers
477 views

Why won't this differential amplifier work without these two additional resistors?

I'm trying to measure a differential voltage in LTSpice using the following structure: The simulation results are correct, the voltage at the output is very similar to the differential input voltage. ...
FernandoPT's user avatar
2 votes
1 answer
55 views

How to simulate a 30 inch FR-4 lossy channel (20dB loss) using ltline symbol in LtSpice?

For designing a high speed serdes system, I need to model a lossy channel of FR-4 substrate of length as 30 inch and 20dB attenuation. How can I implement it in LtSpice tool?
MEGOPI's user avatar
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3 answers
529 views

How can we drive an 8 ohm speaker if it can only support around 1.5-2 watts for an Audio Amplifier Circuit?

Goal of the circuit: Must be able to deliver 1.5 W to the speaker (8 Ω) at 1 kHz. First Problem 1.) how can we drive an 8 ohm speaker if it can only support around 1.5-2 watts? Because when we input ...
jaxillrplusone's user avatar
1 vote
1 answer
98 views

Circuit Simplification of (Series/parallel sources)

The question asks to find $$I_s \space\space and \space\space I_x$$ However, before doing so, I should simplify the circuit. Is my simplification correct? (I.e. is tripling the value of I_s and ...
Nero's user avatar
  • 113
5 votes
1 answer
690 views

What causes these spikes in an LTspice circuit analysis of a full adder?

For the following full adder circuit: I get the following output for s (I have the same problem with COUT): The graph itself is correct, but those spikes should not be there. I know that I have to ...
Jake's user avatar
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1 vote
0 answers
111 views

Op-amp circuit and simulation

I solved the following circuit (by which I mean finding the output voltage) and I tried simulating it to check my results. This is the main circuit, without the op-amp power supply connected: And ...
Wolfuryo's user avatar
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1 vote
0 answers
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Having trouble simulating a two-stage differential amplifier in LTspice

The following is an LTspice simulation for a two-stage differential amplifier. The simulation takes hours. What am I doing wrong? Spice netlist: ...
kile's user avatar
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1 vote
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MOSFET parasitic turn-on

I'm simulating a circuit which uses a high-voltage SiC N-channel FET to discharge a large voltage (something close to the breakdown voltage of the FET, 1.7 kV). The power supply for the circuit is a 1 ...
L30LVC's user avatar
  • 21
2 votes
2 answers
65 views

simulation output impedance of ADA4522-1

I have been trying to simulate the output impedance of ADA4522-1 using LTSpice. I have added a sinusoidal voltage source with 1Vp-p voltage at 1MHz at the output and connected the input to ground ...
Fateme's user avatar
  • 181
2 votes
1 answer
63 views

How would I create an analog block function in LTSpice?

I'm trying to create a small-signal model of a PSFB converter in LTSpice. The blocks in red are what I am trying to create, essentially a multiplier block which computes various .PARAM parameters that ...
user353165's user avatar
1 vote
0 answers
53 views

How do you fix this 'unlabeled value' error?

I'm really new at this and I can't understand what value is not labeled here.
andg23's user avatar
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1 answer
75 views

How do I configure a negative clamper in LTspice?

I am trying to make a negative clamper in LTspice. The pulse source goes from 10V to -10V harmonically. My aim is to lower it's voltage by 7.3V, so it will have a pulse graph going from 2.7 to -17.3V, ...
Pascal's user avatar
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0 votes
2 answers
106 views

Bizarre behavior with SIN LTSpice

I have this circuit I'm supposed to analyze. I am asked to set v1 to a sine wave V1= A sin (2pi f t) with a frequency f = 1 kHz and A = 5mV. I think I did everything right, but when I run the ...
Jake's user avatar
  • 113
4 votes
1 answer
342 views

LTspice: simulating temperature

I want to simulate the effect of temperature on a semiconductor. I can use .temp ... or .option temp ... or ...
hennep's user avatar
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1 vote
2 answers
86 views

How can I draw these circuits in LTspice?

I am new to electronic circuits and I don't know how to draw these circuits. I can draw some basic closed circuits but I never understood these open ones. Would really appreciate if someone can help ...
Pascal's user avatar
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1 vote
0 answers
208 views

How do I properly import a .lib description into a LTspice symbol?

I am trying to simulate the TI part TPS62808 in LTspice, Pspice for TI, and Tina TI. I managed to easily run the simulation in the latter two simulators, but the models were specifically made for them,...
Yordan Aleksandrov's user avatar
1 vote
1 answer
79 views

Differential output resistance with LTSpice

I have a simple NMOS FET where I would like to plot the differential output resistance at the operating point of Vgs = 1.7V (which is the Vgs voltage for Id=9.4mA) I managed to plot the output ...
Stefan Wyss's user avatar
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0 answers
27 views

LTspice Simulations with PCB parameter Tamb = 75 C vs on-board MOSFET working at 75 C comparisons

I have built up LTspice simulation model for DC2786A. I want to have the self heating effects of the MOSFETs and check how the efficiency of the converter is affected. But for the junction temperature ...
pod's user avatar
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1 vote
0 answers
75 views

LM27762 voltage regulator LTspice simulation error

LM27762 datasheet I imported the latest model from the Design tools & simulation for the component. I used the following layout from the datasheet as reference, capacitor values as defined in ...
AuFries's user avatar
  • 63
2 votes
1 answer
75 views

LTspice exception: Time step is too small in flip flop simulation

I have scheme with simple JK-trigger with Reset and Preset: But, I have error: Time step too small; initial timepoint; trouble with and-instance A7 (it can say any AND gate) when try to start ...
Everything's user avatar
3 votes
2 answers
142 views

Wrong LTspice simulation results when circuit has a large common mode potential to ground node

I'm trying to simulate the effects of a common mode signal on an optically isolated analog input circuit. I was seeing terrible common mode rejection ratios no matter what changes I made, and ...
jms's user avatar
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2 votes
1 answer
122 views

LTspice model file for new component

I would like to add some new components to the LTspice library. I have never done this before. The online SPICE forum discusses 3rd party component steps. It says I have to download the SPICE model ...
David Ab's user avatar
  • 129
3 votes
1 answer
119 views

Need regulated 15 kV output

I was just playing around with this ZVS circuit I made in LTspice. It was made to output 15 kV, but when I saw its actual output it had spikes of 25 kV, then it stabilized after a while. How to ...
user012484's user avatar
1 vote
1 answer
70 views

Floating node of amplifier in LTSpice

I have been trying to create an actively loaded degenerated CS amplifier with current mirror in LTSpice and whilst working on other aspects of the amplifier the Vout node decided it was floating. I'm ...
EEE22's user avatar
  • 21
2 votes
1 answer
140 views

How can I add an LM567 in LTspice? [duplicate]

From searching the web it seems it is not included with the installation of LTspice, so I will have to add it as a 3rd-party model. I am fairly new to LTspice and I'm not sure how to do this as I ...
Jason Crosby's user avatar
1 vote
2 answers
134 views

LTspice IV: Stability of op-amp circuits

I am studying the stability of op-amp circuits using LTspice with the help of this video. I can see many threads on Stack Exchange like this one, but the explanation is not clear to me. I have a ...
Hari's user avatar
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0 votes
1 answer
122 views

LTspice - auto-transformer impedance ratio

Can you please clarify what formula is used by LTspice to calculate the auto-transformer impedance transfer ratio for the equivalent circuits below? Both circuits resonate on the same frequency. I ...
andrzej's user avatar
  • 11
3 votes
1 answer
230 views

Failed to simulate active current mirror in LTspice

The following is my schematic for active current mirror: This is a SPICE simulation for my old question: The following is the \$V_{out}\$ plot. What's wrong with my \$V_{out}\$? The asc file is ...
kile's user avatar
  • 776
1 vote
1 answer
133 views

LTspice inrush current simulation

I'm trying to simulate the inrush current of a system that I measured with an oscilloscope before. In my simulation I have a voltage bouncing effect on the wire between the supply and the Rshunt that ...
SteveninJ's user avatar
1 vote
1 answer
204 views

Creating third order butterworth filter with Sallen–Key topology

I am trying to design a third order Butterworth filter with Sallen–Key topology. I am quite new to this and there is not much only about third order variations.I have the following requirements: Gain:...
confusionpersonified's user avatar
0 votes
0 answers
41 views

LTspice induction motor model

I'm trying to simulate the dynamic model for induction motor in (alpha, beta) stator axis. Results are not correct but I don't know how to fix this issue. How can I fix them? Code: ...
ppinha's user avatar
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1 vote
1 answer
78 views

DC-DC converter possible by using Zener breakdown as input to transistor gate?

Suppose you have a DC voltage source that is higher than required, in this example let's assume one wants a 12V voltage source from a 18V source. Would it be possible to have a circuit, where the ...
luksen's user avatar
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3 votes
2 answers
371 views

LTspice showing wrong voltage

I am trying to get this circuit to work correctly. I am following a book, and according to Ohm's law this resistor should be 350 Ω to get 2 V at the LED. I am only seeing around 800 mV. To get around ...
Jason Crosby's user avatar
1 vote
1 answer
66 views

How can I use the external library for the 2EDF7175F Gate Driver by Infineon in LTSpice?

I want to simulate a circuit including the Infineon 2EDF7175F (Gate Driver) in LTSpice 17. This is my circuit: I created both the irfl024z (Mosfet) and the 2EDF7175F by opening the .lib in LTSpice ...
Till's user avatar
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0 votes
1 answer
98 views

LTspice simulation

The Zener diode is an LM385-BZ 2.5. I could not find that SPICE model, so the circuit is running on standard values. The first picture below with Vout = 0-3.3 V is what I am trying to get, but the ...
luffy's user avatar
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-2 votes
2 answers
175 views

Impulse response ltspice

Is any one able to explain why I am not getting an impulse response when I probe across L1? The voltage shown seems to be the same no matter where I probe on the circuit.
confusionpersonified's user avatar
2 votes
1 answer
91 views

VOM617AT SPICE model not working

I downloaded the VOM617AT (optocoupler) SPICE model from the following address: https://www.mouser.com/ProductDetail/Vishay-Semiconductors/VOM617AT?qs=9vrc9xEJKyxW%252B%2FlvaQ%252BSPg%3D%3D I am not ...
nmr's user avatar
  • 123
1 vote
1 answer
201 views

CD4007-based subthreshold MOS amplifier

I'm considering buying a pair of CD4007 ICs so that I might build a subthreshold NMOS amplifier. I've seen it discussed here. I'd like to build this circuit depicting a simple subthreshold amplifier. ...
Virgil_Tibbs's user avatar

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