# Questions tagged [modeling]

This tag covers finding models for electrical and electronic components and circuits

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### Mathematical models for vacuum tubes?

Are there any commonly accepted algebraic models for vacuum tube operation (triode, tetrode, and pentode)? In the same way that BJTs have a Gummel-Poon or Ebers-Moll model, and (macroscale) MOSFETs ...
23k views

### How do I construct a SPICE model from a data-sheet?

This may not be the ideal forum for the question; please migrate if a forum is better suited for the question. I'm looking at a component for which my attempts at locating a SPICE model online were ...
895 views

### How, if at all, can a memristor be emulated with active components?

I find existing explanations of memristors are either overly vague, or an unapproachable mass of academic, mathematical analysis. I want to gain an intuitive understanding of what a memristor is, what ...
842 views

### What causes this knee in my MOSFET drain voltage drop?

FINAL UPDATE: Understand a previously mysterious power MOSFET switching waveform wiggle! @Mario uncovered the root cause here below, distinctive to so-called VDMOS devices, typical of many power ...
918 views

### Does anyone use op-amps for modelling physical systems any more?

I am studying for my System Modelling and Simulation exam. So the textbook says there are three categories of models. Graphical - block diagrams and signal flow graphs. Physical - physical similarity ...
1k views

### Simulation model for floating gate

I am designing a non-volatile memory cell and foundry does not have model for floating gate . So I used the Voltage controlled current source to mimic floating gate. For output characteristics, I ...
1k views

### Modelling MEMS accelerometer's measurement noise using datasheet (ADXL330)

I'd like to model an Analog Devices ADXL330 MEMS accelerometer using data provided in its datasheet to estimate measurement noise. I'm using a simple mathematical model defined in the paper "Non-...
215 views

### Operation of BJT with low values of Vbe (“cutoff” region)

Many sources claim that when the base-emitter voltage becomes smaller than approximately 0.6V-0.7V, the bipolar junction transistor goes in the cutoff region and there is zero base and collector ...
10k views

### What is a typical diode's ideality factor?

Some background, for anyone unfamiliar: The Shockley diode equation is $I_D=I_S·(e^{\frac{V_D}{n·V_T}}-1)$ with the quantity $n$ called the ideality factor, a number between 1 and 2. Ideal ...
1k views

### Push current source through transfromer

This lecture (from page 130) shows manipulation of the buck-boost converter model into canonical form. I am stucked at moving current source through transformer as in the picture below or from the ...
2k views

### Modeling long wires in circuits

What's the proper way to model really long wires in circuits (18ga, ~1500 ft)? I'm aware that over long lengths start to accrue non-ignorable resistances. I'm wondering if they start to get other ...
2k views

### Av for small signal analysis with BJT for unbypassed emitter and ro in place

My question is about another question on this site. On that question Z(in) for small signal analysis with BJT for unbypassed emitter and r0 in place Zin is asked for a common emitter configuration ...
247 views

### Modeling scalar control of PMSM

I have met with a scalar control algorithm for a permanent magnet synchronous motor. I haven´t heard about it before so I decided to develop a dynamic model to further analyze this control algorithm. ...
968 views

### How is possible that with same Ibase there is more than one Vce?

Ok guys, look at this picture: How is possible that with the same $I_{\rm base}$ we have more than one $V_{\rm ce}$?
5k views

### Input Characteristics of MOSFET in triode region?

When a MOSFET is operating in saturation region, i.e. $V_{GS} > V_{th}$ and $V_{DS} ≥ ( V_{GS} – V_{th} )$, the drain current equation clearly indicates the parabolic relation between the drain ...
376 views

### What is conductor to conductor to shield capacitance?

I am using 6.5 ft (2 meters) BELDEN 9154 shielded twisted pair cable for a sub 1 MHz application and I wanted to make a model of the cable for some simulations. The datasheet of the cable lists two ...
102 views

### Voltage spreading to resistors network

I want to model several electrodes (say 3) and GND on a resistive substrate. simulate this circuit – Schematic created using CircuitLab To characterise it, I apply a current on one electrode ...
4k views

### Modeling a solar panel for simulations

I need to simulate a power conversion system (using SIMetrix/SIMPLIS) in which solar energy is captured by a solar panel, which is then connected to an inverter for supplying current to the grid. ...
755 views

### Antenna modeling software and tutorials

I'm starting to learn about antenna theory, feedlines, and different types of matching. I can build antennas etc from plans but I would like to be able to design my own and understand their ...
105 views

### Appropriate model of an unknown sonar piezo

I have a collection of piezoelectric transducers that I have got from old devices. No print stamp on them, and I couldn't get a schematic of the device that could help me to find a datasheet. I ...
2k views

### Modeling passive elements at high frequencies

It is well-known that any electrical passive element (Resistor, Capacitor,Inductor) contains parasitics that usually manifest themselves at high frequency ranges of operation. For example, a resistor ...
2k views

### MOSFET input capacitance variation with Vgs

Let's consider the classic FET push pull Class-AB follower. simulate this circuit – Schematic created using CircuitLab The DC operating point is determined by output voltage and output current,...
752 views

### Solar cell electrical model from datasheet

I would like to build an electrical model for a solar cell based on its datasheet specifications. As an example, I retrieved one from Digi-Key: http://ixapps.ixys.com/DataSheet/SLMD480H12L-DATA-SHEET....
50 views

### Abstract signal and noise model for a logarithmic image sensor

A conventional grayscale image sensor pixel can be modeled as a "light bucket." Photons arrive on the sensor pixel for a fixed exposure time. The light bucket fills up with photo-electrons linearly ...
162 views

### How can I model a double pendulum in op-amps? [closed]

I'm interested in chaotic circuits; and while many circuits that model attractors like Chua's Circuit, Lorenz Attractor, and RC phase shift networks are available, I would really like to model the ...
156 views

### Basic MOSFET modelling question

I have a basic question regarding silicon-based MOSFETs and alternative MOSFETs such as InGaAs. I am aware of the fundamental equations in which describe the current flow for the silicon channel ...
806 views

### Unrecognized and ignored parameters in LTspice while adding a Third-party model

I have tried to add a third party model to my LTspice program (2016 version) but when I run the simulation many errors show up. The model is made for PMOS and NMOS ( saved at the same link) Link of ...
102 views

### Does the Shockley diode equation apply to Schottky diodes and non-silicon diodes?

As I'm sure most people here know, the Shockley diode equation is $$I_d=I_s[e^{\frac{V_d}{nV_t}}-1]$$ Notice that none of the quantities here other than $I_s$ and $n$ are dependent on the diode ...
63 views

### In practice, what is the difference between the “nominal plant model” and the “plant model”?

I am reading a book on nonlinear control and disturbance rejection, and in many examples, they distinguish between the "plant model" $G_p(s)$ and the "nominal plant model" $G_p(s)$. They also add ...
787 views

### Measuring BJT (Ebers-Moll) parameters

I am currently attempting to measure the parameters of a "vintage" germanium BJT in the hope of creating an Ebers-Moll model from the data. So far I have been unable to find a comprehensive source on ...
2k views

### Can the Ids equation of MOSFETs be applied to real devices?

In my engineering course, we have studied MOSFETs a lot, and always in the context of integrated circuits. And what we have been teached is that (in the basic approximation), its current is given by (...
174 views

### diode equivalent circuit model AC analysis

I've understood the small-signal analysis for the diode, like how is the value for rd derived. But here are somethings i don't understand: How is capacitance of the diode dependent on the frequency ...
3k views

### Passing user parameters into a custom PSpice model

I am building my own simulation parts in Orcad 16.6: I can build a schematic and take the generated netlist to use as a stand-alone component, but I want to be able to change parameters inside the ...
1k views

### Mathematical model of the temperature of resistors/heatsinks?

I want to model the transfer function of a resistor mathematically, and am after some resources / tips on if it's possible to do so. For example, if I put 1V into a 1 Ohm resistor, I want to know how ...
1k views

### VLSI: RC Modeling of a digital CMOS circuit

The simple RC-model for mos transistors in digital circuits, brought in CMOS VLSI Design book by West-Harris is like this: But in other sample of book a 3-Input nand gate modeled like below: When I ...
18 views

### How to fix ngspice simulation of Cree XLAMP CXB1507

I'm trying to simulate the 36V Cree XLAMP CXB1507 (spice model) using kicad+ngspice. When I try simulate it gives the following error: .model cxb1507 36v d is=6.15257e-19 n=32.22321 rs=9.82504 xti=...
3k 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 ...
169 views

### Modeling a long single wire in a circuit?

I'm currently trying to make a model (equivalent circuit) of a long single wire with a resistor and inductor in series. Is this a proper way to do it? What I have done: Calculating the resistance ...
99 views

### Modeling Photovoltaic Devices

In this video the man present this schematic (at 6:20): And he say that you've to add some capacitors but I don't understand why. I've to model a solar-cell and I have to use the most complete ...
1k views

### Finding transfer function of DC motor

I am trying to find the transfer function of a DC motor experimentally using the step response method, for that I am using the following circuit: Hooking up to Fin a transmissive photosensor that is ...
2k views

### Brushless motor controlled via current source math model

I'd like to model a brushless motor's (BLDC) dynamic response using Matlab. I'm controlling the motor by an Elesctonic Speed Controller (ESC). I'd like to derive a transfer function of such a circuit ...
807 views

### State diagram Implementation

I am trying to develop a state machine model for my current firmware design. I searched google, but the explanations are not related to embedded system. Can you please suggest some method to study ...
42 views

### Making a model of a transformer

According to this link, the equivelent circuit diagram of a transformer (seen from the secondary side) looks like: Now, I want to find the values of the following constants: R_p,X_p,R_c,X_m,R_s,...
584 views

### What is the syntax for modelling a non-linear element in Spice?

Suppose I have the following circuit. My question is how do I write the net-list in LTSpice such that f(i) = i^2 + 2 (for example) ? I couldn't find the syntax on the internet.
5k views

### Modeling the elevator as a finite state machine

This is my first post here. Nice to meet you all! I've read a related question here and am still having issues. The task: There is a building consisting of 7 storeys (indexed 0-6). Design a system ...
2k views

### State space modeling with disturbances using Matlab

I am doing a project which involves modeling a quadcopter in state space form using matlab. I first had to linearize the quadcopter equations of motion, and now have to implement them in a matlab ...
975 views

### DC Motor inertia voltage drop

following a tutorial on the web I created in LTSpice a DC motor model, but I have a question about the results, the model is: and this is the spice netlist: ...
9k views

### Z(in) for small signal analysis with BJT for unbypassed emitter and r0 in place

I have been studying the small signal analysis of BJT with re model with the emitter terminal not bypassed. I am able to derive those Zi, Zo,Av, Ai long as ro is assumed to be infinite. But I am ...