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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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Confusion with Bode plot in LTspice when using a voltage regulator

To experiment(out of curiosity) the effect of a low pass filter for an SMPS switching noise I wanted to try a filter where an LC cascaded by a linear regulator as shown in below diagram, I obtained ...
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2answers
64 views

Obtain a Transfer Function from Bode Plot shown

I want to obtain a Transfer Function from the Bode Plots I already got the corner frequencies (approximates) and all the terms for my T.F. Then when I try to check my results in MATLAB my plot drops ...
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34 views

Is my measurement setup correct for the common mode frequency response?

I’m using a USB scope which can be used as also a network analyzer. For a network like a passive filter, to obtain Bode plots one input channel is set for reference the other as output. And the input ...
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1answer
300 views

What does actually the “unravel branch wrap” option do to the phase plot in LTspice?

Below two Bode plots are identical just that in the second one the option "unravel branch wrap" is unticked for the phase plot: What does this option do to the phase plot?
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45 views

Whats the difference between bode plot linear and cartesian?

As in title, Whats the difference between bode plot linear and cartesian in LTspice? In both cases i get V(f) but the values differ. Which plot will give me values of voltage at given frequency that ...
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2answers
175 views

Low Pass Filter Wrong Pole Location

I wanted to understand and derive an equation of simple low pass filter that shows the location of pole in frequency response graph (Bode plot). So, here is the derivation: $$V_{OUT}=\frac{V_{IN}*...
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2answers
81 views

Bode Phase Plot of RC High-Pass Filter

I have been trying to understand Bode Phase Plot of RC High pass filter. I know that from my engineering that voltage lags behind the current passing through the ...
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0answers
36 views

System requirement in frequency domain

Hi Can any one help understanding and interpreting figure 6a and 6b (page 6) in the paper attached down bellow : I need to identify first the transfer function of each plot and then interpret system ...
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1answer
53 views

Dynamic Compensator in Control Loop

Sorry if this has been asked previously, but I couldn't find anything here or elsewhere on Google (but maybe I'm searching the wrong terms). I'm trying to design a Type 2 compensator for a PWM chip I'...
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1answer
46 views

Determining Phase Boost needed to Compensate SMPS

I'm attempting to find the Control-To-Output Bode Plot (open-loop) of a SMPS designed around the TPS54160 so that I can design the type II compensator. The first step in designing a compensator is ...
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1answer
38 views

Bode Plots - Absolute Value of Complex Function in Magnitude calculation

I'm struggling with one step in the magnitude calculation during manual Bode plotting. Specifically during the step of applying the absolute value to \$s = jw\$, what is the reasoning for why you can ...
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1answer
89 views

Loop Gain and Phase Margin Correlation

I have found a definition of phase margin of amplifier system from Texas Instruments application report. This definition looks like this: $$\phi = tan^{-1} (A \beta)$$ where \$ A\$ is amplifiers open-...
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1answer
109 views

Bode plot graph: Frequency vs. Angular frequency

I am wondering, why are some Bode plots made with \$f\$ or frequency of signal representing x-axis, and why other Bode plots use \$\omega\$ or angular frequency of signal representing x-axis? Why don'...
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2answers
125 views

How to define a transfer function for a given system?

I just finished reading this paper, on how to "draw" Bode plot for a given transfer function. After done reading I realized that it would be pointless to learn this stuff, if I wouldn't know how to ...
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1answer
34 views

Bode magnitude computation

Consider the following transfer function $$ G(s)=\frac{1\times 10^6\, s}{s+1} $$ If I evaluate the dB magnitude analytically at frequency 0.1 rad/s, we have $$ \text{Mag. at 0.1 rad/s} = 20\, \log \...
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1answer
45 views

Understanding log-log axes

In below picture there are two graphs representing the function \$H(s) = s-z_1\$ (assume \$z_1=2\$ is a constant). The left graph has \$\omega\$ on x axis and \$\|H(j\omega)\|\$ on y axis. The right ...
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2answers
342 views

How to determine the phase margin and transfer function of this bode plot?

I have some struggles to find the transfer function of this plot. We got the hint, that the "breaks" of slope can be assumed to be on vertical and horizontal lines. Also we should pay attention on the ...
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30 views

determine the cutoff frequency of a nMOS in common gate with gate resistance

I have to determine the upper cutoff frequency of this circuit. I absolutely mustn't use the laplace domain because it's too time consuming so not compatible with the time I have at the exam. A rapid ...
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2answers
215 views

Quality Factor and Cut-off Frequency Defintion

Suppose we have $$ H(s) = \dfrac{ k \frac{\omega_o}{Q}s}{s^2 + \frac{\omega_o}{Q}s + \omega_n^2}$$ What is the definition of the quality factor? My understanding is that it is the gain at the cut-...
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4answers
75 views

How do I integrate a function and plot the result on Matlab?

I need to plot a function that has an integrate inside, but I don't know how to do this on Matlab. Function: \$ SOC(t)= SOC(0) - \dfrac{1}{Q}\int_{0}^{t}i_2(t)dt \$ time is in hours, current is in ...
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2answers
80 views

RC Filter measured response differs from calculated transfer function

I've created a first-order RC filter with R = 68 Ohm, C = 5.0 uF, and I am studying the transfer function of this filter. I have calculated the transfer function to be 1/(1+jwRC), based on the ...
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2answers
96 views

Poles and Zeros of Two Pole Compensation

I am known with the basics of what poles and zeros of transfer function are and how to determine them, but I certainly don't know how to apply such poles and zeros to the gain curve, which describes ...
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2answers
345 views

How to calculate, *for a square wave input*, the cut-off frequency point for a basic RC low pass filter with

I am applying low pass filter for a pcb circuit I am trying to design (picture below). I have managed to calculate the cutoff for a sine wave input since I can insert a frequency (i.e. f_c = 720 Hz ) ...
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6answers
139 views

A weird question about the cutoff point of an RC low pass filter

I have read the linked explanation about the RC low pass filter circuit and understood most of it. I understand the relation between the time constant RC to 1/(2*pi*f_c). I understand it means there ...
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1answer
97 views

Gain of proportional Controller with distubance \$sin(10t)\$

The diagram below represents the position of ocean oil platform system which use the proportional controller with gain \$k\$. The output \$x(s)\$ is the platform deflection regards the position ...
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1answer
72 views

How to plot the open-loop gain of an inverting amp, difference amp, and low pass filter?

For example, if we are using the ADA4004-1 op amp in all these circuits, the open loop gain is 400000 as shown in the spec sheet (Table 2): ADA4004 Datasheet The open-loop breakpoint is at 30 Hz (...
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247 views

Speed of response and crossover frequency relationship

In SISO(Single Input Single output) cases, My professor keeps mentioning the speed of response and crossover frequency interchangeably. I don't really understand what the speed of response means also ?...
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1answer
52 views

Can't draw bode curve of this zero

I have a transfer function like this: \$H(s)=\frac{s^2+\frac{1}{LC}}{s^2+s\frac{R}{L}+\frac{1}{LC}}\$ I can separate the denominator into an expression of the type: \$(1+s/a)(1+s/b)\$ and then plot ...
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2answers
140 views

dc to dc converter bypass capacitor consideration

I using a TI buck regulator (LM21212) to power a bunch of components on my board at a certain voltage. When calculating stability, do I need to take into account all the decoupling capacitors (e.g. 0....
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3answers
87 views

What form for Transfer Functions to use for filters and Bode plots?

I've seen some different forms for the equation of a transfer function and wonder which one is most correct and why? Does it depend on type of filter etc.? Let's take an example and its transfer ...
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1answer
180 views

RHP zero with a positive phase shift

All books and references I read say that RHP zero gives a negative phase shift. I can infer that by plot the phase of the function \$w_{z}-s\$ where \$w_{z}>0\$. With this function, when frequency ...
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1answer
162 views

Why does my cutoff frequency not match the 3db down point?

My understanding is that the cutoff frequency of this circuit can be calculated simply by: 1/(2*pirc) I get a cutoff frequency of 15.9kHz But as is shown in the provided bode plot 15.9kHz is ...
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How to specify the correct phase shift of special transfer functions ?

I know how to construct the Bode diagrams of first order and seconde order(Complexe conjugate) transfer functions. But here in the two examples below i confront some difficulties. I hope someone can ...
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2answers
286 views

Draw the amplitude and phase diagram through the transfer function

My function in terms of s (Laplace variable) is: $$G(s)=\frac{1000(s+200)}{(s+20)(s+2000)}$$ The calculations I've done so far: $$G(s)=\frac{1000(s+200)}{(s+20)(s+2000)}=\frac{\frac{1000}{11}}{s+20}...
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42 views

Bode Plot Asymptotic Approach Questions

Consider the step-by-step asymptotic approach for drawing Bode plots given on the last page here. I had two questions about using this approach by hand (instead of adding individual graphs to find the ...
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deriving the transfer function given bode plot

I have been given the following question on finding the transfer function from the following bode plot I know that the transfer function should look like this \begin{equation} H\left(jw\right)\:=\:\...
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7answers
630 views

Practical ways to obtain Bode plots for an unknown circuit

I want to use a practical method/way where I can obtain roughly the Bode plot of a system especially a filter. This of course can be done by using complex math or implementing the circuit in a SPICE ...
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1answer
57 views

How to find the frequency of more than one zeroes analytically?

Hello, I have to draw the Bode plot of \$G(s)=\frac{V_u}{V_{in}}\$ and I want to do it without calculating the full transfer function. This circuit has Cgd=1pF capacitors at every Mos. Vt=0.4V, k=2mA/...
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103 views

What to use in finding frequency response : \$G(s) \cdot H(s) \$ or \$ \dfrac{G(s)}{1 + G(s) \cdot H(s)}\$?

While studying frequency response of control systems, all of the sources I'm referring to is considering unity feedback system i. e. H(s) = 1 & drawing Bode plots and polar plots on basis of that. ...
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1answer
53 views

Can somone please put into layman's terms how a TF affects a Bode diagram?

I'm given the TF of a system, and I can figure out the magnitude for the Bode plot (just switch to jw and grind out for the requested w), but I don't understand in layman's terms how a transfer ...
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2answers
1k views

Design of Butterworth high-pass filter

I am trying to design, and later implement, a Butterworth high-pass filter with a cut-off frequency of 8kHz and a decay rate of 60dB/decade. For this filter \$ \omega_c = 50265.4824 rad/s\$ (...
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3answers
819 views

Controller to increase phase or gain margin

I can't find any good sources on this one. The only textbook I have says nothing about it. I've been restricted to the use of some formulas given by our teacher which I don't understand why they ...
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1answer
217 views

Increasing frequency response instead of gain for a Cascode circuit

so this a homework problem that I am working on and I'm not looking for a flat out answer, just a good place to start and some help on the concept. So the question is as follows: Suppose our ...
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3answers
507 views

Phase margin measured at lowest positive-gain point, rather than 0dB point?

When discussing voltage regulators, one often hears that phase margin should be measured at the 0dB gain crossing. This makes intuitive sense in a simple system where the phase has only a negative ...
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2answers
4k views

Find transfer function from Bode plot

This is my Bode plot The solution manual says the function plotted is $$\frac{s^2+0.02s+1001}{s^2+2s+101)(s^2+20s+10100)}$$ What I know is the Bode plot for $$\frac{s^2+2ζω_ns+ω_n^2}{ω_n^2}$$ and the ...
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3answers
210 views

criteria to select 180 degree as a c

why we choose -180 degree as a critical point for bode plot? i want the explanation for why we choose the factor 180 degree i.e,****above 180 degree represents instability and below 180 degree ...
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2answers
228 views

criteria to consider 180 degree as phase cross over frequency in bode plot

Why 180 degree is taken as phase cross over frequency in bode plot? In bode plot, grid impedance(Zg) and inverter impedance(Zi) is plotted for both magnitude and phase. The frequency at which Zg and ...
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2answers
338 views

A confusion about a transfer function's Bode plot and s domain view

Recently I have been stuck with a simple Bode plot and H(s) comparison. To begin with, here is the transfer function: H(s) = 1/s For Bode plots I write: H(jw) = (jω)^-1 = 1/(jω) For the magnitude ...
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2answers
3k views

What exactly is Pole Frequency in a Filter and how does it affect the frequency response?

I'm having great trouble understanding the concept of a pole in a real world electric circuit. I do understand what a 'pole' is and what a 'zero' is, in the point of view of a 'Transfer Function' but ...
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2answers
563 views

Open loop gain - understanding the simulations

I tried to simulate a non inverting amplifier, to see the differences from the amplification up to the unity gain, just to learn to be more confident with the LT Spice tool. Then I saw this video ...