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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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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81 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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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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87 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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45 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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63 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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36 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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48 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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73 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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445 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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121 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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132 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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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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42 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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70 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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82 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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54 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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39 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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42 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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102 views

Help deriving the transfer function of an LC circuit?

I have the LC circuit below. I believe (but I'm not certain) that this is a 3rd order filter. Since there are two capacitors and 1 inductor. The circuit is a passive low pass pi filter. The ...
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60 views

What does 'passband phase' and 'stopband phase' mean?

I've been provided with a Bode plot for an RC filter circuit with a cutoff frequency of 10kHz. Im asked to find the stopband and passband phase from the graph. I'm confused how these can be just a ...
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1answer
39 views

MOSFET Differential Amplifier Bode Plot

I've created a MOSFET Differential Amplifier in PSpice, the schematic of which I've attached. However, when doing an AC sweep and adding a trace to do a Bode plot, the graph is a flat line, and I don'...
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What does a Bode plot represent and what is a pole and zero of a Bode plot?

I studied Bode plots and the author of my book is somehow relating zeros of transfer functions to Bode plots. What is the relation between zeros or poles of a Bode plot and transfer function? We ...
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181 views

How to find the cutoff frequency of an underdamped second order lowpass filter

I've learned that for a first order LPF the 3dB frequency is one where the amp's gain is (surprise) -3dB below the DC gain. However, on a second order LPF that is underdamped we get a "peak" at around ...
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73 views

Poles from Bode plot

How does one deduct the number of poles from a Bode plot? Is it further possible to decide where the poles are? I have not understood this concept even though there is so much focus on Bode plots in ...
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39 views

Octave bode plot looks like a decade plot in LTSpice

When I do a bode plot on a load over a simple LRC filter then compare graphing the frequency in OCT and DEC, I would expect their plot shapes would look different given OCT plots the x-axis in 1Hz,2Hz,...
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60 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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84 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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94 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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39 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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124 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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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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145 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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88 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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84 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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128 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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63 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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79 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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90 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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174 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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137 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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186 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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68 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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85 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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98 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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71 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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136 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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37 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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