Questions tagged [spice]

A famous textual circuit simulator with a number of graphic front-ends. Please tag with the precise flavor used (e.g. Pspice, LTspice, ngspice, Multisim, Proteus, Qucs) whenever appropriate (e.g. syntax or debugging) because there are substantive differences between implementations.

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31 views

Constant power load SPICE model

I would like to create a SPICE model for a constant power load. I'm guessing that would involve using an equation to dynamically adjust the model's resistance based on the applied voltage. How do you ...
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33 views

Charging a capacitor in Eagle SPICE

I'm trying to learn the basics of Eagle SPICE simulation with a simple capacitor charging circuit. My netlist is as follows: ...
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1answer
47 views

Testing spice model for common mode rejection ratio?

I've been trying to create a circuit to simulate common mode rejection ratio of an op amp to test the spice model's accuracy. While I've seen online that being able to use exact resistors only a ...
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25 views

Test circuits for testing input and output capacitance of an NMOS spice model?

As the title states, I'm having trouble finding resources online for confirming the capacitances of an N-MOS spice model. If there are any resources someone could point me to to learn more or test ...
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24 views

How can I simulate “definitions” (DEF/ENDDEF) and to draw (DRAW/ENDDRAW) on LTspice, is it possible?

I have the circuit XR2211 described on "definition" with the commands DEF and ENDDEF, and drawn with the command DRAW and ENDDRAW. Working simulations in LTspice there are many information, but this ...
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1answer
49 views

Need help with 2 Transistor Current Limiter Circuit in LTSpice

I am new to LTSpice. I have attached a picture of my circuit below: The goal of the circuit is to provide current to the R1 until It is too high. Then the BJT will activate, shutting the FET off. ...
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27 views

DC DC converter simulation time slow in lt spice

Usually I can 'finagle' DC to DC converter simulations into working in a timely manner, this one has me stumped. I have done the standard gmin/abstol/reltol/cshunt combination, set initial conditions ...
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66 views

Test cases for for OTA in LTSpice

Here is a component OTA provided by LTSpice which has inverting non inverting common and output node. I am in process of modelling this OTA behavior form LTSpice to PSpice. I reffered this link for ...
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26 views

Eliminate external pin in SPICE netlist

I'm working with a SPICE model of a MOSFET that provides a fourth pin for setting the device temperature (driving the pin with a voltage in simulation sets the temperature). However, I don't plan on ...
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40 views

Altium Designer 19 mixed simulation

I'm trying to plot a current vs. resistance graph using mixed simulation in Altium Designer 19.1.5. I'm having a problem creating the variables and plots which are not against time. It would be very ...
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2answers
81 views

How can I get FROM and TO times of trig on measure statement of LTSPICE?

I need to measure the voltage on two signals which have a difference of phase, so in order to do the measure that I need I have to get V1 (t) and V2 (t + delay_between_signals). One way to that is by ...
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1answer
59 views

How to assign the same value to multiple resistors in an LTSPICE circuit

I have around 10 resistors in a circuit, all with the default value "R". I defined the directive .param R=100 Upon running the simulation, I get the error ...
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46 views

LTSpice error with V() function, … when referencing net within a subckt (V(subCktName.NetName))

I've converted an IBIS model to a SPICE model using microCap, and am trying to simulate that subckt with LTSpice. Using LTspice, I get an error with the subckt in the library. "u1:g1: Unknown ...
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29 views

Pulse frequency modulation mode in buck converter MAX15062

I am modelling MAX15062 DC-DC buck converter using datasheet in PSpice, initially i worked on control loop. This buck converter has two modes PWM and PFM mode. With MODE pin unconnected works on PFM ...
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47 views

LTSpice error with the V() function in a subcircuit

I'm trying to do a simulation with a subcircuit, and I've narrowed down the issue to the V() function. The simulation fails with the message 'can't find definition of model "V" ' Here is the spice ...
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3answers
831 views

LT Spice Voltage Output

I am using LT Spice for simulation of my circuit. I have used a probe to check for the voltage on the Capacitor. What is the green dotted line that can be seen in the plot? Thank you.
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244 views

How do I import a spice model into LT spice?

I decided to create a question of how to import models into LT spice since there were questions that are related but no definitive guide on how to import 3rd party models on this site. There are many ...
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24 views

Constant current limit in the SIMPLIS

I wanted to convert this error amplifier form Pspice to SIMPLIS, for now i am using voltage controlled current source (VSCS) with the FB nod to the negative and Vref to the positive node of the device ...
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3answers
112 views

Sine Wave Input for Op Amp Integrator but Output Looks Weird

The input is in sine form (AC input) but the output (in blue color) is the straight line. So what is wrong with my schematic in LT Spice this time? I thought I should've got output in sine form if I ...
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1answer
87 views

Simulation on LTSpice

LTSpice does not have a gap sensor as a component. Is there anyway I can either download a gap sensor or is there a way to create my own one.
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24 views

2:4 Decoder on LTSpice [duplicate]

LTSpice does not have a decoder component so I have had to make my own using two inverters and four AND gates. I am not sure if I have done it correctly.
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11 views

Simulation of decoders on LTSpice [duplicate]

I need to simulate a 2:4 decoder on LTSpice however the component does not exist. Does anyone know of a way to simulate it?
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44 views

Simulation of decoder on LTSpice

I need to simulate a 2:4 decoder on LTSpice however I can not find the component anywhere. Does anyone know of a way I can simulate it?
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79 views

opamp constant-gm bias circuit

I try to incorporate the constant-gm bias circuit (Figure 6 in Improvements_in_biasing_and_compensation_of_CMOS_opamp) into the PFC (positive feedback frequency compensation) opamp, but it resulted in ...
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2answers
770 views

If Manufacturer spice model and Datasheet give different values which should I use?

I'm trying to simulate an LED circuit but I am getting a large difference in results from the simulation vs calculations done using the datasheet information. In this case both the spice model and ...
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1answer
61 views

NTC Project (Wheatstone Bridge + Instrumentation Amplifier) - Stuck!

I've been lurking through these forums for years but just now had the urge to ask for help. I'm creating a thermometer (using an NTC thermistor) for my college project. I began to analyze my sensor ...
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1answer
40 views

Is a circuit simulation package available with models from multiple vendors?

I need to simulate a filter that will be used with a DAC. I need to model noise, accuracy, and drift to calculate ENOB and identify tradeoffs. I have used LTSpice for my modeling needs for the last 10 ...
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81 views

If I need to find an MOSFET spice model with a particular length and width, where do I start?

I was using a 180nm NMOS and PMOS but now need to use an NMOS with about L=.36u and W=100u. I have two models but I dont think I can just change the length and width to any value. How can I check if ...
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2answers
113 views

SPICE BJT simulation results

I'm trying to simulate simple BJT circuits to verify my hand calculations. Following is my circuit, I'm just trying to get the calculated DC collector current with the shown voltages and parameters. ...
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3answers
1k views

Strange opamp's output impedance in spice

I'm simulating this circuit in Micro-Cap, which is the clipping stage of a guitar effect. The opamp model is the "NE-5532" I want to measure the input and the output impedance. I expected an output ...
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1answer
72 views

Voltage Multiplier Problem

I´m working on a voltage multiplier with 5 stage, i´m using the same capacitor and i think that my problem is the current load but i actually think that with a resistor in the output of the multiplier ...
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16 views

spectre save command - usage

I did look at save command documentation in Spectre user and reference guide. But it still looks confusing to me. I am specifically looking for commands to do following two task: 1) probe all nodes ...
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77 views

Transient Noise Analysis in HSPICE using Monte Carlo simulation while preserving process variation

I want to analyze the effect of noise on a simple transistor circuit using HSPICE, while maintaining process variation. The basic setup is as follows: The HSPICE models for the transistors are ...
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51 views

Performance issues when using CMOS SR Latch with 180nm transistor models in circuit simulator

I am trying to incorporate a CMOS SR latch made with 180nm Level +49 transistors into a larger circuit but am running into issues. I am hoping this community can point me in the right direction of ...
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1answer
123 views

How do I model a resistor array in SPICE?

I am currently building a library of SPICE simulation models that is going to include resistor arrays. These arrays exhibits both absolute tolerances and relative tolerances. Usually, the relative ...
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28 views

How to calculate or show in matlab/pspice the DC component from a circuit simulation?

Based on Pspice I'm simulating this RL full wave rectifier That gives the next voltage and current output at the showed probe point The idea is to extract the DC component of the current or voltage, ...
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2answers
243 views

Plot voltage for different resistor values in LTSpice

I've signed up for a SPICE course at work, that will take place on Monday and I'm desperately trying to learn electronics and SPICE. (I work as an embedded engineer but with very lacking electronics ...
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76 views

NMOS current flowing equally in both directions in SPICE simulation

I am trying to characterize this nmos on Xyce simulator (and trying to change its present Vthreshold) and am first DC sweeping the gate and measuring the current through the nmos. I run into this ...
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101 views

LTSPICE Model Parameters of P-MOSFET

I am trying to simulate a circuit including TSM500P02CX P-MOSFET. The manufacturer of the MOSFET doesn't provide SPICE Model, so ...
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1answer
41 views

Linear regulator operating point over input DC Sweep analysis

I'm sweeping the linear regulator input voltage on DC using Spice from 0V to maximum expected Vin. However, as the OTA that makes part of LDO is internally supplied by the output voltage, the ...
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2answers
89 views

Error in third-party SPICE subckt of a MOSFET

I am simulating my circuit having a DMG1012T N-Channel MOSFET in LTSPICE XVII. My Circuit is given below: However, after ...
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2answers
191 views

How to automatically “normalise” a voltage signal in LTspice?

I would like to create an output signal that is normalised by the maximum value of a signal in LTspice. This is to produce a signal between [-1, 1] that is suitable for producing a wave file like ...
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2answers
96 views

SparkFun Sound Detector Circuit Analysis

I would like to request some help in analyzing the op-amp circuit used by SparkFun here. I'm particularly interested in the pre-amplifier portion of this design. The write-up included by SparkFun ...
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54 views

TI Photodiode Trans impedance amplifier Circuit?

I am designing a Photodiode(Vishay/ current of 15uA) circuit amplifier (TI ) in SIMetrix. frequency of Photodiode is 1MHz. I choose an Amplifier from TI as OPA355_Q1(spice model imported from TI) and ...
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2answers
108 views

Colpitts values for NXP's SA605?

I'm trying to put together a simple superhet radio, receiving at 161.75MHz (this is for AIS reception.) I've been trying to design around NXP's SA605 chip (see SA605) but I'm having a hard time ...
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62 views

zero AC gain of CMOS inverter

Why is the following AC analysis of CMOS inverter resulted in zero AC gain (vout/vin) ?
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44 views

dc sweep convergence issue for cmos inverter

I am having some convergence issue with DC sweep for a CMOS inverter. To duplicate the exact issue, see the following log as well as the attached netlist files, together with modelcard.nmos and ...
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2answers
72 views

Howto debug ngspice error PPerror: syntax error during transient analysis

In an effort to better understand software and how my computer actually works I have been experimenting with simple electronic circuits. I am working up to having three two bit registers (A, B, C) ...
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104 views

VCVS in LTSpice Operating as a Comparator

I am using a VCVS in LTSPICE. I am confused about the command in the Spiceline for using a Table. I want to use the VCVS as a 1 bit Comparator instead of making a transistor based one. What will ...
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3answers
113 views

Measuring transconductance of any circuit

May I know if the following transconductance measurement test circuit is correct because I am getting quite small Gm values ? I suspect that I need to use some derivative function because changing ...