Electrical Engineering Stack Exchange
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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.

Anything related to Bode plots, i.e. a special graphical representation of the frequency response of a linear time-invariant system, which is a complex-valued function of frequency describing how the systems reacts to sinusoidal signals of different frequency.

The frequency response \$H(f)\$ of a system is related to (and sometimes mistakenly confused with) its transfer function \$G(s)\$ by the formula:

$$ H(f) = G(j 2 \pi f) $$

Bode plots are the plots of the amplitude (in decibels) and phase components of the complex-valued function \$H(f)\$ versus frequency (this latter in logarithmic units), i.e.:

The plots of $$ 20\;log_{10}|H(f)| $$ and $$ arg(H(f)) $$ versus logarithmic frequency are the Bode magnitude plot and the Bode phase plot respectively.

See also Wikipedia on Bode plots.

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What are some insights from looking at Bode plots

After studying this in school, the entire concept of a Bode plot still seems to be as a bit of a let down for me given how much emphasis is placed upon it, how often this tool is rumored to be used in the workplace and how little it actually seems…
Fraïssé
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Gain margin and Phase Margin Physical Meaning

I have been trying to understand the physical concept of Gain and Phase Margin. What I understand about this is that a relative comparison around the critical point \$(-1,0)\$, which when converted to magnitude and phase form turns out Magnitude =…
Fawaz
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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 simulator. But these requires knowing the circuit…
user16307
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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 usually take zeros at \$s=-a\$ (let's say) but how…
Ali Aqdas
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Why a low-pass filter applied to a square wave gives a weird wave?

When a low-pass filter acts on a square wave, the output is something similar to this: My question is simple. If the filter is a low-pass filter, it should filter all frequencies that are above some constant frequency (the value will depend on the…
felipeek
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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…
JordenSH
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Op amp circuit stability in linear regulator circuit

I am trying to design a stable linear regulator using MOSFET and op amp. Schematics is shown below: I am using LTSpice for simulations. This circuit is mostly for educational purpose: I want to understand how to use bode plots to design a stable op…
Artem
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Interpreting bode plot of type 3 compensation network for buck regulator

I'm struggling to design the type 3 compensation network for a simple buck PWM controller. The controller is a Richtek RT8110B. According to the datasheet, half of the type 3 network is in-built and cannot be changed: Note Rs, Cs, and Cp are…
Dan Laks
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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 -6 dB according to the transfer function. So, am…
Mehdi Ghazavi
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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?
user16307
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Interpretation of mathematicial and corresponding physical meaning of gain and phase margin

In my textbook these are the definition of gain and phase margin: The gain margin is defined as the change in open-loop gain required to make the system unstable. The phase margin is defined as the change in open-loop phase shift required to…
Fraïssé
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What is the transfer function for a first order active high-pass filter

What is the transfer function for the below circuit? simulate this circuit – Schematic created using CircuitLab Since the op-amp has unity gain, the transfer function should be the same as a passive high pass RC filter. This can be found by…
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Why are there ripples in the passband of some filters, like the Chebyshev filter?

Please see the Bode magnitude plot as we steadily increase the input frequency to the filter. Why does the magnitude oscillate? What physical component(s) in the filter circuit is producing that oscillation effect in the magnitude plot? For…
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Draw Bode-Plot of a transfer function

I want to draw the bode plot of a tranfer function: $$ H(j\omega)=\frac{100j\omega T}{j\omega T + 10}, T=1s $$ Now I have $$ H(j\omega)=\frac{100}{1 + \frac{10}{j\omega T}}, T=1s $$ Using a double log…
Sam
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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 slope with increasing frequency. However, what about…
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