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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28 views

How to calculate RC (in 2st RC lpf) that satisfies fc in real circuit

I'm designing a two-stage RC LPF (Low-Pass Filter) and I want a cutoff frequency \$f_c=1000\mathrm{Hz}\$. So, I choose \$R_1=3\mathrm{k\Omega}, R_2=33\mathrm{k\Omega}, C_1=4.7\mathrm{nF}, C_2=47\...
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77 views

Bode plot? H(s)= 1 / (s² +1)

I have transfer function $$H(s)=\frac{1}{s^2+1}$$ When I put that in Wolfram Alpha I get that there is peak on Bode plot at 1 and it is 60dB. Why? There is no damping here... Usually in formula ...
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33 views

Why 180 degrees of phase margin should be considered?

We've had one feedback on the phase difference, with the gain as 1. At 300 to 60 degrees, there's just a phase difference, and 61 to 299 degrees, the output is larger. Shouldn't we consider an angle ...
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34 views

Why the sum of the responses of s and s increase with 20dB per decade or 40dB per decade?

I am not sure by how much will the response of the function H(s) = s^2 increase?
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30 views

Is it possible to sketch a bode plot for a discrete-time transfer function?

For a regular s-domain transfer function, there are simple rules you can use to draw an asymptotic bode graph, basically by taking a slope of +/-20dB per decade and a phase shift of +/-90 degree for ...
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54 views

bode plot: calculating number of decades away from a cutoff frequency

(From "Circuit Analysis Demystified", David McMahon, 2008, Chapter 15, Example 15-6, and Example 16-7) Let's say I have a Butterworth filter with cutoff frequency: $$\omega_c$$ The stop band ...
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1answer
61 views

Phase margin for a system (design of PD controller)

I have a system with the following transfer function: \$G(s)=\cfrac{20}{s^2+s+20K_f}\$ where \$K_f=1.75\$ I want to use a PD controller and I want obtain a phase margin of 35 degrees. I need to ...
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50 views

How do i find poles and zeros from a Bode plot?

I have this Bode plot of CS amplifier but what I need is poles and zeros of the circuit. I am using Pspice for simulation. And the Bode plot is: Now, I calculated the poles theoretically and the ...
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1answer
66 views

A two-pole system can never be unstable?

I was reading in some textbooks and places online that a single pole introduces a -90 degree phase shift and that in the phase plot, it never actually reaches -90, it goes asymtotic to it. Similarly, ...
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1answer
85 views

Does this high-bandwidth transimpedance amplifier ring (Multisim)?

I designed a front-end for the S5972 high-speed photodiode. See the following schematic. In Multisim an AC sweep analysis gives the following Bode plot: 1. Is the presented front-end stable? If not, ...
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42 views

drawing bode plot and the meaning of the amplitude and phase

I'm having trouble understanding how to infer from the transfer function amplitude how to draw the bode plot. i.e given the following transfer function: Is the amplitude is the slope of the graph? ...
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53 views

Why is my LC filter Bode flattening out to 20dB/dec in my Simscape simulation?

I just made an LC filter Matlab Simulink simulation and I don’t know why the Bode diagram is flattening out. After the resonance it falls steeply, but after that it sets at 20dB/decade. Shouldn't it ...
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63 views

Bode Plots and Electrical Circuits - Zeroes and Poles

I would like to understand more electrically with little math (transfer function) involved regarding Poles and Zeroes in a control system (Feedback in DC-DC Buck Converter to be specific). I ...
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1answer
96 views

LTspice not getting exactly -3dB point

Looking to answer another question on this site, to did some math and fired up LTspice to check some values and I am not able to the -3dB point. I found the transfer function to be $$ H(s) = \cfrac{...
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106 views

How to design analogue compensation for SMPS from Bode Plots?

In a complicated switched mode power supply where the transfer function is unknown, is there a way to design an analogue controller and compensation from the bode plot alone? I am having difficulty ...
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1answer
76 views

Bode plot gives negative stability margins for a stable plant

I have a plant whose transfer function has all the poles in the left half of the s-plane (obtained the poles using Wolfram Alpha). However, its bode plot gives negative phase and gain margins; I ...
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1answer
60 views

How to determine the transform function of certain bode plots?

The answer to this question above is C, yet I only know that the anti-resonance and resonance are located at 8 and 11 Hz respectively. Another example below to which the answer is B. I appreciate ...
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2answers
77 views

Drawing the Bode Plot of a loop gain

Below I have the loop gain and the Bode plot for it, however I do not understand the phase plot. Why does it start at -90 degrees instead of 90 degrees since we have a zero? Please explain.
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71 views

Nyquist Plot from Bode Plot

How do I know the value at which the Nyquist plot crosses -180 degrees from looking at the Phase plot from the Bode?
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63 views

Sketch a Bode Plot for the Loop Gain of the circuit

Below I have the transfer function, but I am still uncertain about Bode plots. How do I know the slope, how do I know where the zeros of the function are?
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1answer
57 views

Cutoff frequency of transfer function at -6 dB

I'm trying to design a second order low-pass filter using the following transfer function: \$\ H(s)=\frac{f_c^2}{s^2 + 2 f_c s +f_c^2} \$ with cutoff frequency fc = 3400 Hz Whenever I plot this, ...
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29 views

Error amplifier in PWM controller

Using the datasheet UC3842 PWM Controller I have modelled error amplifier in it. AC analysis of error amplifier matches with the datasheet plot(Figure 3) - Since I need to clamp the output ...
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1answer
86 views

How do i draw the bode plot for H(s) = 100000 ∙ (s + 10) ^3 /( s ∙ (s + 100) ∙ (s + 1000j) ∙ (s − 1000j))

How do i draw the bode plot for $$ H(s) = \frac{100000(s + 10) ^3 }{s(s + 100)(s + 1000j)(s − 1000j)} $$ I searched tutorials for the Bode plot, theory and tutorials but i can't find a solved or ...
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168 views

Phase margin is 90 degrees but transient step response shows overshoot

The bode plot of the loop is as shown here The transient step response looks like this The block diagram looks something like this - Basically a single stage opamp(OPAMP in fig) with high gain(...
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57 views

How to design a high pass filter given a stopband and cutoff frequency? [duplicate]

I have fs = 132 Hz and fc = 770 Hz I want to design a first order high pass filter that increases gain at a rate of 20dB per decade from 132 Hz until 770 Hz. Before 132 Hz the filter must stay ...
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1answer
62 views

Transfer function G(s)= 2/(0.0625*s^2+0.1*s+1) phase calculation problem for ω>ωn

I am trying to create a table of values and the bode plot for the tranfer function G(s)= 2/(0.0625*s^2 + 0.1*s + 1). However when i use values above ω{n} the the values of phase does not agree with ...
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62 views

Interpreting this bode plot

I ran a frequency analysis on a conductive textile I have designed and I am not sure what to make of this bode plot. My background is in textile design, not engineering. Does this make sense to anyone ...
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45 views

What is this functions Phase crossover frequency?

OLTF loop gain My approach What I have done wrong?
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159 views

How to find Phase crossover frequency?

I make the imaginary part of \$loop \ gain=0\$ to find phase crossover frequency. But in one video, the person told that this method can only be applied when Polar plot crosses the real axis and ...
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2answers
252 views

Why is LTSpice Bode plot disagreeing with a linear plot?

Here is a picture of an amplifier that I'm simulating using LTSpice. When I insert a sine wave of 0.01 volts and 314Hz as an input, I get this: The output is taken from the collector and is ...
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2answers
62 views

Are phase angles in filter transfer functions primarily for stability?

I see transfer functions and bode plots (magnitude and phase) and it occurred to me, that I don't really use the phase plots at all. My career experience seems to have gotten away without having to ...
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1answer
240 views

Audio Equalizer LTSpice Simulation

First, I'd like to say i'm not experienced on circuits, but i'm doing my best to learn. I'm trying to create an audio equalizer which is capable of amplifying low frequencies (20Hz-200Hz), mid ...
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57 views

Bode diagram calculating for random frequency

The max Gain of an opamp is 100dB (=100000). I have a cutting frequency at 10 Hz and then the slope of my bode diagram decrease by -20dB/dec . I have unity gain at 1MHz. For 100 Hz its increasing by ...
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3answers
120 views

Bode diagram for RL circuit

I am trying to create Bode diagram for the following circuit: First I create the transfer function, I arrive to a point that looks like this (C is not capacity, sorry for bad name choice): I don't ...
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278 views

Proof of Bode-Fano criterion

I was reading this thesis and it mentions Bode-Fano criterion almost in every chapter of this thesis. Could anyone advise about the derivation of bode-fano criterion? Note: The original proof is so ...
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202 views

How to sketch the Bode diagram of the output filter of a Buck converter?

I'm trying to figure out the Bode diagram of the output filter of a Buck converter: simulate this circuit – Schematic created using CircuitLab Vout is ...
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1answer
324 views

How can I export the frequency response from LTSPICE without phase wrapping?

After I plotted the frequency response of a circuit using LTSpice as shown: I exported the plots data as a .txt file in order to plot them after that using MATLAB, however, after I plotted the data ...
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346 views

LTSpice: Produce Bode Plot for Compensated & Uncompensated Boost Converter

I am designing a product which uses the LTC3122 as a 5V-12V boost converter (datasheet here). This particular device provides the ability to add gain compensation, phase lead, or both. In my case I am ...
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1answer
51 views

Gain deficit and phase margin at crossover

I went through an exercise of the following specifications: A voltage mode buck converter working in CCM mode works with: \$V_{in}\$ min = 10V, \$V_{in}\$ max = 20V \$R_{load}\$ min = 2.5 ohm \$R_{...
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1answer
90 views

Does frequency at zero matter?

Consider the following simulate this circuit – Schematic created using CircuitLab $$ H(s) = \frac{sR_2C_1}{1+s(R_1+R_2)C_1}$$ $$ f_z = \frac{1}{2\pi R_2C_1} $$ $$ f_p = \frac{1}{2\pi (R_1+R_2)...
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1answer
163 views

How is H(jw) = jw correspond to a slope on bode plot?

I cant understand how H(jw) = jw always intersects at "1" , also how the slope of the line is 20dB, Kindly explain, im having a hard time understanding because in book such stuff is not discussed,only ...
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372 views

Plotting bode plot, how the starting gain is in negative?

For function; \$H(jw)=10jw/((1+jw/2)*(1+jw/10)\$ To find starting gain, i did, \$20log(10)\$ which equals 20, but in matlab, it shows ...
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2answers
77 views

Why is the Bode plot of 1/s a straight line?

The magnitude of the impedance of a capacitor is \$(\omega C)^{-1}\$. Plotting the impedance vs frequency should be a curve with slope \$-1/(\omega ^2C)\$. Why is it plotted as a straight line with a ...
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1answer
128 views

Why Deliyannis bandpass filter with high Q does not have the expected transfer function bode plot

What i need is to design a delyiannis band-pass filter with Q enhancement technique. The theoretical analysis of this technique is referred here in pages 107-112. For those who don't know how to ...
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36 views

Choosing a position sensor (encoder) and obtaining velocity from it

How do I know how many counts per revolution I need for an encoder for my application? I need to be able to accurately capture a 1000 Hz signal on an input side running from 1-133 rev/sec (60-8000 ...
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3answers
293 views

Nodal analysis -> transfer function -> step response

I've been trying to get the transfer function for the circuit in the image below, but I seem to be doing something wrong, since the simulation on Circuitlab gives me a different Bode plot and I can't ...
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1answer
360 views

How to estimate the transfer function given only Bode plot data points?

I'm trying to obtain transfer function given Bode plot data points. As an example I used the following RC filter and made AC sweep as follows: I set the type of sweep to decade and for each decade ...
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1answer
241 views

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
422 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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1answer
83 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 ...