What is Bode plot: Definition and 76 Discussions

In electrical engineering and control theory, a Bode plot is a graph of the frequency response of a system. It is usually a combination of a Bode magnitude plot, expressing the magnitude (usually in decibels) of the frequency response, and a Bode phase plot, expressing the phase shift.
As originally conceived by Hendrik Wade Bode in the 1930s, the plot is an asymptotic approximation of the frequency response, using straight line segments.

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  1. guyvsdcsniper

    Engineering Bode Plot Slope based on frequencies

    From 0 to ##10^3## ##\omega## there is a dB gain, from ##10^3## to ##10^5## there is another. Finally from ##10^5## to infinity the slope is constant (0). I know the formula $$dbV= 20log_{10}\frac{V_2}{V_1}$$ can give me the slope but that is in terms of Volts, but I have frequency and the...
  2. A

    Inverting op amp frequency response Bode plot help

    Using analog discovery 2 kit and the bode plot produced by the network analyzer is off. The scope looks fine and everything is behaving how it should except for the bode plot. The magnitude of the bode plot will start at the correct dB then right before tapering off it shoots up a few dB and...
  3. P

    LTSpice functionalities regarding its Frequency Domain Analysis

    The time domain analysis is easier to plot compared to analyzing the frequency with respect to the phase. But, LTSpice makes it look really easy. So, for a small signal AC analysis, LTSpice does use a AC voltage source for its frequency domain analysis function. This must be a really convenient...
  4. garthenar

    Engineering W0 = 1/RC? Transfer Functions and Bode Plots

    Here is the example and solution in full. I have circled where I'm at and highlighted the part that's tripping me up. I managed to get... and getting everything in terms of the angular frequency seems to be critical for getting the plots for the Frequency Response. I checked my notes on RC...
  5. P

    Engineering Bode plot for active low pass filters

    Hi Can anyone help with this? I understand what the bode plots should look like but I am not sure how to produce a plot in excel for them without any values The transfer functions are: Vout/Vin = 1/(SQRT(1+(ω/ωc)^2) and Vout/Vin = -G/(1+j(ω/ωc)) As both are first order filters they will have...
  6. Y

    Scalar in terms of multiple variables, Nyquist & Bode Plot

    Homework Statement A scalar is given by It is controlled by With step time h = 0.2 s 1. Find the discrete equivalent model 2. Check the stability of closed loop (K = +1) 3. Obtain the via the Bode plot Homework EquationsThe Attempt at a Solution So for question 1. This is where I'm...
  7. W

    Third Order High Pass Filter (Report)

    Homework Statement [/B] The filters of FIGURE 4(a) to (c) where designed using a commercial software package (http://focus.ti.com/docs/toolsw/folders/print/filterpro.html) Write a report (of approximately 750 words) that discusses and compares the design of each filter in terms of their...
  8. Cocoleia

    Asymptotic magnitude Bode plot for a network function

    Homework Statement I am working on the following problem: The Attempt at a Solution I have the solutions, I just don't understand: I know that the pole should be the root of the denominator? but in all the examples I was given they used s and not jw, so what is the variable in the network...
  9. kostoglotov

    How transfer functions become Bode plots

    Homework Statement I have a question related to taking the logs of transfer functions, getting the individual Bode plots of each subsequent factor, and adding those plots graphically. I'm working from Fundamentals of Electric Circuits, 5th edt. Let me start with the following screen capture...
  10. Mohamed_Wael

    Determine the natural frequencies experimentally

    How can we determine the system properties (natural frequencies & damping ratio ) practically using forced vibration? One way is to measure the phase angle, using the bode plot, the exciting frequency corresponding to 90 (deg) phase shift should be the natural frequency, are there any other...
  11. G

    What is a problem of my graph?(frequency response)

    I have drawn a bode plot(freauency response), but it is not the same with one which is attatched in paper. Using this data, I have drawn the graph using matlab. I just put data into second order vibratoion system which is given in the paper(eq 18) Peak location of graph in paper is just in...
  12. S

    How can i read this Bode plot?

    I think that first peak of the graph represent a resonance frequeny but i don`t know some peaks which are located after first peak. Is it a just noise? or some other?
  13. S

    Bode Plot Application: Increase Frequency Response & Magnitude Understanding

    Hello, After long time i am able to find Laplace transform function but can't understand the bode plot which give information of frequency response and magnitude i think plaese anyway here how can push my thinking ahead in it?
  14. J

    Bode Plot Notation: Gain & Phase Margins Explained

    Hi, i was just wondering if someone would be able to tell me what ωπ means when finding the gain and phase margins on a bode plot?
  15. J

    Bode Plot Method For a Transfer Function

    Hi , I was hoping you could look at this link and let me know if I have interpreted the method correctly http://i.imgur.com/5axTiBN.jpg As I understand it the transfer function has had s replaced by jw but also the top and bottom are divided by 10 - This is so that the brackets on the bottom...
  16. L

    How do you do a Bode plot comparison with LTSpice?

    I'm trying to use LTSpice in order to fine tune LC circuits, but a road block I've hit is that when I run the simulation and generate a bode plot, the previous plot is overwritten, so I can't visually compare the effects of the L C changes. Some graphing programs have a function that let's you...
  17. A

    Identifying type of feedback by looking at bode plot

    Homework Statement Below is the bode plot of return difference, 1+C(S)P(S) in a feedback system. Identify the frequencies where the feedback is large, negative, positive and negligible. P(S) = \frac{100}{s^2+2s+1} C(S) = \frac{220(s+50)}{s+200} Homework Equations Bode Plot, Feedback The...
  18. A

    Effect of Phase Lead Compensator on Phase and Gain margins

    Homework Statement What is the effect on the phase and gain margins of a system when a Phase Lead Controller/Compensator is added? Homework Equations I have designed the phase lead controller for the system so if anyone wants to see it, please ask The Attempt at a Solution I know, that in...
  19. U

    Plotting Bode of Resistor w/ DC Source: 20*log(0)

    I am ploting bode of resistor connected with DC source.So no freqvancy at all! The bode magnitude plot should be(or it should start from) 20*log(jw)=20*log(0) (jw=0 because we have dc source) what should be the value??for step of 5v... what should bode look like??
  20. H

    Translating from Japanese: residue in capacitor?

    So, I have made an experiment of a low pass filter, and made a bode plot out of it. My experiment was done 100 percent in Japanese and this means I cannot understand completely the experiment I have done. So, there is a statement there saying the higher the frequency of the input voltage, the...
  21. LTME

    Controls - gain margin question

    Homework Statement Find the Bode Plot, and the phase and gain margins for the uncompensated system. Homework Equations G = (3.6s+6)/(s(.1s^2+.7s+1)) The Attempt at a Solution I understand the phase and gain margin ideas, but the gain margin hinges on the phase crossing -180 degrees, and in...
  22. gfd43tg

    Bode plot and stability margins

    Homework Statement Homework EquationsThe Attempt at a Solution Hello, In part (b), I found ##k_{cu} = 0.5##. I found in part (d) a controller gain of ##k_{c} = -0.3## yielded a diverging output. Here are the bode plots for parts (a),(c), and (d). I don't understand how I should use the...
  23. Rectifier

    Bode plot for first order high pass (RL) - reality vs theory

    Hey there! So I have this circuit: with R= 1kOhm and L=10mH and for some reason the theoretical and real values differ drasticly for lower frequencies Brown lines are representing the asymptotic and approximation lines. Blue lines are connecting my measured values. Amplitude is the amplitude...
  24. T

    Sketch Bode Plot for $\frac{0.5}{1 - \frac{3145j}{w}}

    Homework Statement \frac{0.5}{1 - \frac{3145j}{w}} , sketch the bode plot Homework EquationsThe Attempt at a Solution Moving the jw to the bottom \frac{0.5}{1+ \frac{3145}{jw}} Let s = jw \frac{0.5}{1+ \frac{3145}{s}} = \frac{0.5}{\frac{s+3145}{s}} = (0.5) \frac{s}{s+3145} =...
  25. W

    Extracting information from a Bode Plot (PM, GM, etc...)

    Hi all, 1. Homework Statement http://imgur.com/kqZK1Vv This is the loop gain (A.F.) of unity feedback system. I need to extract DC Gain Bandwidth GBW (is GBW Gain Bandwith ?) f unity (I suppose this is unity frequency) Phase Margin Gain Margin What is the optimal PM and f2/GBW for time and...
  26. J

    Sampling Time Calculation for Bode Plots: Plant Comparison & ZOH Preceding

    Homework Statement In the figure, the Bode plots of a continuous-time plant (thin line) and of its discrete-time counterpart, representing the discrete-time operation of the plant preceded by a Zero Order Hold (ZOH) (bold line), are displayed. What is the Sampling time used? Homework...
  27. J

    How to Draw a Bode Plot from a Given Transfer Function with a Zero at s=1

    Homework Statement Hi, I'm given a transfer function, and am suppose to draw Bode plot from it. H(s) = ( 2000s (s - 1) ) / (s + 2000)^2 I'm wondering what to do for the zero at s = 1? Should I just solve this normally, as every example we have done and every example I've seen uses simple...
  28. A

    Engineering Creating a Bode Plot for a Series RC High Pass Filter

    Homework Statement Make a blode plot of a series RC high pass filter (log(gain) vs. f)... Homework Equations log(Gain)=log(Vout/Vin) I'm pretty sure the "Gain" is just the transfer function, for a highpass it should be the V_in = Vsupply, and V_out = V_capacitor. The Attempt at a Solution I...
  29. S

    Transfer function and Bode plot

    Homework Statement Find the transfer function for the filter on the attached picture and sketch it in Bode diagram, if you know ##Q_0 =\frac{\omega _0L}{R}>>1## and ##\omega _0^2=\frac{1}{LC}##. Homework EquationsThe Attempt at a Solution If I am not mistaken, we defined the transfer...
  30. R

    Bode Plot Matlab Homework: High Pass Filter

    Homework Statement I'm trying to make a theoretical Bode plot of a High pass filter (made up of a capacitor and a resistor). The transfer function is: ##T=\frac{V_{out}}{V_{in}}= \frac{R}{R+1/(j\omega C)} = \frac{1}{1-j\omega_0 / \omega}## With a corner frequency of 5 kHz or in...
  31. G

    Solving Bode Plot Questions: Finding the Gain for Accurate Magnitude Response

    Hello, I have the following problem ( which should be uploaded below the text ) I've done part a) correct, I know how to sketch the bode plots but don't know how to find the gain in order to draw correct magnitute response bode plot. This is where I am stucked and if I find out how to find...
  32. I

    What is the significance of using a log scale in bode plots?

    How did they get the blue box? I know where they got the 0.5 inside the brackets from but not sure about the rest. The bode plot in my data book has log10(wt) as the x-axis..
  33. gfd43tg

    Bode plot with given transfer function

    Homework Statement Homework Equations The Attempt at a Solution Hello, I am having serious problems being able to draw bode plots. At first the professor said to put everything into standard form with an (ω/ω_c)...and then there is also a table in the textbook with standard forms that don't...
  34. R

    What is the Frequency for Unity Loop Gain in Low-Pass Amplifier with Feedback?

    Homework Statement I need some help with the following problem (it is from an old test paper). Below is the Bode plot of the open loop gain of an amplifier: A constant fraction β=0.1 of the output is fed back to the input. This feedback does not load the amplifier. Using the Bode plot...
  35. D

    Solving the Question: Bode Plot and Equation Example for Homework

    Bode Plot It's The biggest one in the entire universe! Homework Statement The question is stated at the top of the image below. Did I answer the TWO questions with this image? https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-frc3/t1/1891009_10151901549150919_346181425_n.jpg...
  36. K

    About bode plot horizontal axis question

    I have a question I'm wondering in bode plot we write the horizontal axis w rad/sec what does this mean? is it normal scale 0.1 0.2 0.3 ... etc with equal distances?? it's clear not because it's drwan on semilog paper if it's the horizontal log w why then we write 0.1 ,0.2 ,,1 ...
  37. F

    How Do You Determine the Critical Frequency in a Bode Plot Equation?

    Given an equation like 2/((jw)^2 +54jw +44), how would you find the critical frequency? I am getting a umaginary number and I am sure this is not true, please help!
  38. Femme_physics

    How Do You Draw a Bode Plot for a Given Transfer Function?

    Homework Statement Given this function in an open loop control system http://img255.imageshack.us/img255/3686/700qa.jpg Draw a bode plot of the transfer function: The upper graph will present the lines for each of the amplification factors for each of the system components, the lower...
  39. A

    Engineering Understanding Circuit Analysis from a Bode Plot

    Homework Statement http://www.wifstrand.se/Albert/stuff/p13.3-6.png Homework Equations From circuit analysis I've found the network function to be H(ω) = -(10^(-4) +jωC1)/(1/R2 + jωC2) (could be wrong) The Attempt at a Solution I don't know how to determine the network...
  40. J

    Calculating Transfer Function off Bode Plot?

    Hey guys. I was wondering if anyone could give me some hints or help me understand well how to get transfer functions off bode plots. Here is an example I need to solve: http://i1226.photobucket.com/albums/ee410/jean28x/bodeplotcalc.jpg
  41. J

    How do I see the gain from this Bode plot? (simple)

    This is the Bode plot of a Broadband Bandreject Op Amp amplifier. The exercise says this: I know that in order to get both cutoff frequencies I need to subtract 3 dB from the plot, but how do I get the gain? I would think that the gain is 3 dB because it is also the distance between the top of...
  42. S

    Gain bandwidth product from bode plot

    Can anyone tell me how to find the gain bandwidth product from bode plot of a unity gain circuit for the attached bode plot? I hv attached the circuit and bode plot ...
  43. H

    MATLAB Matlab: Butterworth Filter Bode Plot

    I'm stuck on a really simple problem because I haven't done MATLAB in a while. I have transfer functions for nth order lowpass Butterworth Filters: H(jw) = 1/(s + w_c)^n I want to plot the 1st to 5th order filters. How do I input H(jw) into matlab? The tf(num, den) is not efficient in that...
  44. D

    How to find cutoff frequencies from Bode plot?

    Homework Statement http://img832.imageshack.us/img832/7517/captureax.jpg According to the solution, the cutoff frequencies are 1, 20, 80, 500 and 8000. I don't understand how to get those answers by inspecting the plot. Homework Equations None The Attempt at a Solution I think the...
  45. D

    Get transfer function from bode plot

    Homework Statement What is the transfer function described by this bode plot: http://img96.imageshack.us/img96/4775/capturegib.jpg *The answer is 3s, but I don't know where it comes from. Homework Equations None The Attempt at a Solution Correct me if I am wrong. A bode plot is a...
  46. C

    Why Does the Bode Plot of a Type 1 System Show a Damped Slope Initially?

    For a transfer function of G(s) = 100 / (s(s+5)), I'm having trouble finding the initial magnitude in dB. It's a type 1 system. If it was a type 0 system with only (s+5) in the denominator, the initial magnitude would be 20log(nominator/denominator) where s is an element of 0, and would decrease...
  47. M

    Bode plot of transfer function

    Homework Statement I have the transfer function: for the circuit: The component values are know, and are: R1 = 47kΩ R2 = 4K7Ω C = 10nF Homework Equations The Attempt at a Solution I have derivied the transfer function but have become stuck on plotting the bode plot. I understand...
  48. C

    What are the characteristics of a second order bode plot?

    What is the difference between second order zero bode plot and second order pole bode plot?
  49. N

    Magnitude and Phase Bode Plot Help

    Hi all, on a current homework I have been given a transfer function and asked to draw the straight-line (asymptotic) magnitude (dB) and phase (degrees) Bode plot. I first learned Bode plots roughly a year ago, and while being on spring break and my notebook from last year is at school, I'm...