Questions tagged [bode-plot]

Anything related to Bode plots, i.e. a special graphical representation of the frequency response of a linear time-invariant system.

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Is there an alternative to GCV (generator control voltage) to synchronize frequency sweep measurements?

A friend is taking a course in electronics engineering and asked me for help reproducing a lab experiment in frequency sweep measurement techniques. Students build a small RC filter and use a function ...
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43 views

Underlying reasoning behind lead and lag nomenclature of compensation

If \$0<z, \;p\$, the Laplace transform transfer function \$\frac{s+z}{s+p}\$ constitute two distinct types of compensators. If we look at this schematic, \$0<z<p\$ (lead compensation implies ...
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How are the -3dB point and the pole of an op-amp related?

I have been looking at AC frequency responses for op-amps and I was wondering how an op-amp's pole and the frequency at the -3dB point are the same? They both mark the location where the gain starts ...
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unstable systems with positive phase/gain margin

Open loop Phase/Gain margins provide information on how much margin the closed loop system have until it becomes unstable. In other words, how much you can increase the effective loop gain and or ...
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103 views

Bode plot of buck converter incorrect?

So this question is a bit related to my other question on using Pspice to get the required transfer function of the buck converter. Here in this circuit I'm trying to get the open loop transfer ...
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120 views

Don't understand this zero pole plot example

I'm reading a book (see figure 5-12) about (among other things) pole zero plots and there is an example I don't understand. For the schematics and formula below: it adds the following zero pole plots:...
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50 views

How to Make a bode plot of an inverting amplifier?

I am trying to create a bode plot of the open loop gain and the closed loop gain of an inverting amplifier using mathematica. I know the documentation of the bode plot in Mathematica (BodePlot[lsys]) ...
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105 views

Closed loop system stability with Bode

Stability of the closed loop system (with -1 feedback) can be assessed via Bode plot gain/phase margin analysis of its open loop system. How can one deduce stability of the closed loop system directly ...
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53 views

Why is the slope of the op amp graph 20 log (AB) in this application note

I am going through the following guide for op amps : http://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf On page 87 (screenshot attached) there is a bode plot which has got me slightly ...
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VNA Measurement method questions

With the Bode100 from Omicron lab, it is possible to perform different measurement. There are two which I want to discuss. You can find the handbook here. These are : Transmission/reflection on page ...
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34 views

Confusion in cut-off frequency of LTI System

Why cut-off frequency is at (in figure given below) the frequency where $$|M(j\omega)|=0.707=1/√2(D.C gain)$$ But isn't cut-off frequency according to its definition should be at frequency where $$ |...
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20 dB/Decade - Justification

I've read that it is recommended to have 20 dB/Decade slope on the L(jw) magnitude plot of the Bode Diagram at gain crossover. This seems to imply a slope of -1 in dimensionless terms. However, what ...
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Vertical axis of the magnitude Bode plot

Why is the vertical axis in the magnitude Bode plot linear? I am confused because i know that if we want to obtain the magnitude Bode plot of the frequency response, we take the decibel value of the ...
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52 views

Nichols plot confusion

The transfer function is \$F(p)=10/(p^2+2p+1).\$ Using Wolfram Alpha, the Nichols plot shows that the argument \$\to -\pi\$ when \$\omega \to +\infty\$. However, calculating the argument on paper ...
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Recreate “Voltage gain vs Frequency” graph of Op-Amp in LT Spice

I am trying to recreate the "Voltage gain vs Frequency" graph of the LT1037 Op-Amp in LT Spice. According to the datasheet page 6 the graph looks like this: - Trying to recreate this in LT ...
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83 views

Infinite Phase Margin

I have been assigned a control systems problem, where I am supposed to stabilize a system using a controller technique from the frequency domain. When I implemented the system on Matlab and calculated ...
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1answer
549 views

How can a Bode plot be like that?

Can you do explain how to draw a Bode plot with GH(s)? How do I get the slope and intersection point? This is one of the teacher's examples. He drew it but I don't know what it means. Can you explain ...
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64 views

How would the pole and zero frequency expression look like for this transfer function I derived?

This is a practice problem in deriving the transition frequency function for mos and part of the set of questions is to determine the pole and zero frequency expression but this transfer function i ...
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53 views

Could somebody clarify the phase angle and gain of this transfer function?

Suppose a circuit with a transfer function of the form \$A(\omega)=\displaystyle\frac{A_0}{1-\frac{j\omega}{\omega_0}}\$ has \$A_0=-10\; V/V\$ and \$\omega_0=100\;rad/sec.\$ We were asked for the gain ...
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63 views

Oscillation frequency / criteria from Bode plot, negative feedback system

Got a question, which is very integral to a project that I am writing a report for (which I am to hand in soon, so in a hurry). Question: What will my oscillation frequency be? How will it be ...
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46 views

A question about negative phase angles in Bode plots

Looking at the phase Bode plot for the output of a filter as shown below: 1-) Taking the point -460° as an example, can we say that this is equivalent to +100°? 2-) Does that mean the output signal ...
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6answers
1k views

Why is frequency not measured in db in bode's plot?

While drawing bode's graph paper where Y axis is gain given in db while the X axis is frequency given in absolute value but scale used is log. I think the reason for log scale on X axis is to increase ...
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99 views

How is this pole compensated

I have an amplifier in a closed loop, the diagram looks as follows: The DC gain is simple which \$ -Rf/R1 \$. If I make \$ -Rf=2\cdot R1 \$ the the DC gain is two. This is verified using AC analysis ...
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91 views

How to find the total phase of this transfer function

I'd always understood that in a transfer function, every pole contributes -90 degrees in phase and every zero contributes +90 degrees in phase. Based on this assumption, I would expect the following ...
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1answer
68 views

2nd order Sallen-Key low pass filter frequency response

I am trying to implement the following circuit in LTspice for studying the frequency response of the 2nd order Sallen-Key low pass filter for a project. Why am I getting a negative peak in the ...
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57 views

How to understand Bode plot or Bode diagram

I am having difficulty understanding the Bode diagram, which I have understood so far: that depending on the angle of the phase, where the system becomes unstable or stable. I just don't know what the ...
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820 views

Pole zero plot of band reject filter

Here is a band reject filter with its transfer function and bode plot. I don't understand how the pole frequencies and zero frequencies are drawn on the bode plot. Even with the pole and zero ...
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5answers
541 views

Problem with Bode diagram in LTspice

I am working on a buck converter and I want to obtain the Bode diagrams of the open-loop circuit. The below circuit is what I made. However, the DC-gain is -96 dB while it should be very small around -...
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1answer
68 views

Bode Plot: calculating phase change

I need to plot this transfer function When plotting the phase vs frequency graph, I am having problems to calculate the change in phase between 10 and 10^1.5. To my understanding, at frequency=10 the ...
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36 views

Bode plot acting weird with specific op-amp

Hello why is the behavior of this op-amp so weird (OP177).I simulated another op-amp(uA741) with the same biasing and the bode plot looks fine(still i dont get the 80dB amplification i would like, yea ...
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93 views

What information Bode plot does NOT present?

The classic Bode plot (2D Bode) represent value of the transfer function (a complex number) evaluated at \$j\omega\$ (imaginary axis). It provides information on system closed-loop stability margins ...
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94 views

Do we analyze real poles the same way you analyze complex conjugate poles?

So I am analyzing a filter and I came up with the following expression for the transfer function in its canonical form: $$\frac{987654 + 4666.67 s + 1. s^2}{2.48519 \times10^8 + 52316.2 s + s^2}$$ ...
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261 views

What is the bode plot of an inverting op amp if you replace the resistors with caps?

What is the bode plot of an inverting op amp if you replace the resistors with caps? What if you now add a capacitive load to the output? Update: I ran a quick simulation and the bode plot looks as ...
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1answer
62 views

Why bode plot of cascade system is not the sum of subsystems?

I have two subsystems which the transfer functions you could see below as g(s) and h(s). According to some references show below, I found that the bode plot of a cascade system should be the sum of ...
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2answers
102 views

Differentiator cut-off frequency

A practical differentiator has two cut-off frequency but can no longer perform differentiaiton after first cut-off. After first cut-off there is a 20db per decade gain reduction but why does this ...
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1answer
119 views

KHN biquad: why does LTSPICE plot a wrong phase plot for bandpass filter?

I'm studying the KHN biquadratic section and its outputs to obtain a lowpass filter, a highpass filter and a bandpass filter. I simulated the filter using Mathematica and obtained the following plots, ...
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51 views

Having trouble making transfer function from this Bode plot from op Amp datasheet in Mathematica

I am fairly green to control theory. I am trying to reproduce the Open loop transfer function of the LT1X28 op amp in mathematica. I want to get the poles and zeros from the following plots and ...
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82 views

Why is Δt constant in phase shift measurement?

I would like to ask for some help with phase shift plotting. To be precise, with time delay between two waveforms. I am measuring two currents using an oscilloscope. channel A (blue) is my current ...
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673 views

Transfer function of electrical network

I need help with this problem. The transfer function that I found is ((RCS+1)/(2RCS+1)) , but then I cannot go further because the form of T.S is untypical. The typical form of this question is RC ...
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178 views

How to do the bode plot for this function without Matlab?

I want to plot the bode diagram without any software for $$G(s)=\frac{(s-2)}{(s^2+4s+15)(s+2)}$$ I do not know how to deal with the factor of \$s-2\$ I will be appreciate if someone can show me your ...
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272 views

Zeros and poles in the following bode plot

According to the definition, zeros are the frequencies which make transfer function to be zero, and poles are the frequencies which make transfer function to be infinity. The definition can be seen ...
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42 views

Phase margin plot of LDO

For this LDO circuit design at https://github.com/promach/LDO/tree/development , 1) which exact circuit node(s) contributes to the zeroes near 1MHz after removing CL ? 2) If I remove "AC 1" from ...
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49 views

Bode plot display in matlab

I would like to display a bode plot of a buck-boost converter using Matlab, so I got the figure shown below, If we look closer to the phase plot, we see that it starts from 360°. My wish is to make ...
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44 views

Determine output filter using the bode approximation

Given that the carrier frequency Fc and modulation input frequency Fm are known, how would I use the bode approximation to determine an output filter, if the carrier frequency component must receive ...
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82 views

Verification of Sallen Key Design

I have designed this Sallen-Key to give a 2nd order low pass circuit with a cut-off frequency of 150Hz. Another design specification is that R1=R2 and C1=C2. The issue is when simulated on LT-Spice ...
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306 views

How can I find the drain transfer function of a MOSFET on LTSpice?

I am trying to get the drain transfer function of a MOSFET by setting the drain to source voltage as the input and the gate to source voltage as the output. I created the following circuit in LTSpice: ...
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27 views

how to plot on the same bode plot a manual function plot() with function bode()?

I have a a transfer function that I plotted manually using Plot(w,abs(f1(w)))(plotted for a digital filer since I dont have signal toolbox) and I have another function that I used directly bode(f2(s))(...
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328 views

Plotting a bode gain plot with the slope in Excel

I am not an expert in Excel, and therefore, I want to know if there is a way of including the slope (dB/decade) in a bode gain plot in Excel or any free software (that allows to first input the ...
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107 views

How to visually determine the damping ratio when we know the peak amplitude

I am currently trying to understand this example from the book, where it visually calculates the dampening ratio given the peak amplitude as well as the natural frequency. Here is the graph from which ...
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66 views

How to choose the transfer function?

Greetings from a physics student. I have to do an activity which aim is to design a filter in frequency. To do so, I need a transfer function (gain, poles and zeros) that must meet the following ...

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