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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.

58 questions with no upvoted or accepted answers
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90 views

### Butterworth Filter attenuates noticeably in pass-band

The Issue: I am using a Maxim MAX7480 8th order Butterworth low-pass filter to counter any aliasing from a sensor that measures signals up to 3kHz, but I only want up to 1kHz. Thus a critical ...
67 views

### Where is the origin pole in my CM buck SIMPLIS ac simulation?

I know that current mode buck regulators are generally stable as long as they're actually operating in current mode (i.e. the inductor ramp current is large enough to prevent slope compensation from ...
203 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 ...
37 views

### Why do we prefer a cross over slope of -1 (20 dB/decade) for bode plot of power converters?

The video mentions (@12:45), we should ensure the slope at cross over should be around -1 (20 dB/decade). He mentions we can apply phase margin test if this condition is satisfied. As far as I know we ...
46 views

### Boost average current mode control

I have one question about the bode plot of boost average current mode control. Below is my schematic, the circuit is stable. My design is for CCM boost PFC, and the current loop crossover frequency ...
79 views

### Underlying reasoning behind lead and lag nomenclature of compensation

If $0<z, \;p$, the Laplace transform transfer function $\frac{s+z}{s+p}$ constitute two distinct types of compensators. If we look at this schematic, $0<z<p$ (lead compensation) implies ...
1 vote
81 views

### Optimum design of damping LC filter with parallel (R+C). There is a frequency in which value of R dosn't impact

Apologies for the not so clear title, but I don't know if there is a common phrase that describes the point of concern. I am taking an online course about input filter design interfacing the grid and ...
1 vote
164 views

### What are the gain and phase margins from this Bode plot?

I thought I had a decent grip on how Bode plots work yet for this model that I am working on, I need to implement a lead or a lag compensator. A lead compensator, which I was thinking about ...
1 vote
66 views

### Is it okay/valid to have a Bode plot that has linear magnitude scale?

I have almost always seen that the magnitude axis of a Bode plot is in dB but today I was shocked when I saw in LTspice that Linear option was also available for Bode representation. I am very ...
1 vote
66 views

### Is there a methodical way to desig multi-stage anti-aliasing filters?

Lately I've been thinking about the best approach to design multi-stage anti-aliasing filters in real-life. I know tools like Analog Filter Wizard or LTSpice can help to a certain extent, but they've ...
1 vote
162 views

### Nichols plot confusion

The transfer function is $F(p)=10/(p^2+2p+1).$ Using Wolfram Alpha, the Nichols plot shows that the argument $\to -\pi$ when $\omega \to +\infty$. However, calculating the argument on paper ...
1 vote
151 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'...
1 vote
260 views

### Bode plots and electrical circuits - zeroes and poles

I would like to understand electrically with little math (transfer function) involved about poles and zeroes in a control system (feedback in a DC-DC buck converter, to be specific). I have been told ... 1 vote
361 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 (...
1 vote
861 views

### Resonant circuit using LTSpice

I'm a college student and I was supposed to draw the Bode-plot of the following resonant circuit. I obtained this. My questions are: shouldn't I have obtained a bell-shaped curve? How can I find the ...
1 vote
308 views

### power supply frequency response

I have a question regarding the frequency response of a boost converter. I am curious to know what causes the "blip" at around 8kHz that causes the response to go up and then back down. At first, I ...
31 views

### How could we predict the transient response of the multi-loop circuit?

Typically, when analysis the stability of a single loop circuit, we can use the open-loop method, just to break the loop and get the loop gain. Then, using the Bode diagram, we can easily get the PM(...
23 views

### Is it correct to use the concept of phase margin for not so 'well-behaved systems'?

The TI document mentions the Phase margin as 60 degree for the given bode plot whereas the lowest PM when Gain >1 is around 45 degree. Wiki says: " Ordinarily, as frequency increases the ...
34 views

### How to obtain a bode plot for this circuit in Matlab online version

So I've an electrical circuit in matlab as follows: I've already setup the points of linear analysis. But I can't the option for linear analysis in the linearization tab. The problem is that I cannot ...
94 views

### LTspice Bode plot is incorrect or inconsistent (op-amp circuit)

I'm testing the open loop transfer function of an op-amp circuit by following this schematic: This is my LTspice schematic (keep in mind the actual op-amp circuit itself has been thoroughly checked, ...
19 views

### Error during analysis in AWR Microwave Office

How to fix this error, and what does it mean? A port is off grid. All polygon edges with ports attached must be 'snapped' to the grid.
88 views

### Bode plot of second-order system

I was reading about second-order systems in Control systems engineering by Norman Nise and I am confused by the idea that the phase at high frequencies of a second-order system is equal to 180° (check ...
161 views

### Frequency response of LC filter with resistance in parallel with the capacitor

The following is the diagram of interest: The impedance of the filter is: $$Z_o=\frac{R_f L_f s}{R_f L_f C_f s^2+L_f s+R_f}$$ and the bode plot with all different components and the total impedance ...
79 views

### LTI system Bode curve

Given an RLC circuit, I needed to find the transfer function, which I did. Now I need to find R and L so that the next two conditions are met: The overshoot is 25% The first peak time is t = 3 The ...
40 views

### Negative loop gain of LDO

I am trying to design an LDO with the following specification: Vout = 1.5V; Vin = 1.7V - 2V; Iload = 75uA to 1200uA. However, while I am simulating its loop gain, its gain is coming negative. Even ...
96 views

### Frequency response of a cascade opamp circuit using LTSpice

I'm trying to simulate this circuit which consists of multiple stages of op amps, but I couldn't figure out the operating bandwidth of the circuit. Using AC analysis, the Bode plot is a weird shape ...
75 views

### Gain and phase margin interpretation in control system

I have a unity feedback system with the open loop transfer function having the following bode plot: As shown on the plot, the gain margin and phase margin are -27.4937dB and 75.0185 degrees. And the ...