# 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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### Why do some op amps' datasheet specify phase margin at open loop?

I am not able to understand what significance phase margin would hold in case of open loop. Shouldn't it be just phase? If it was loop gain I'd understand specifying phase margin to denote stability. ...
64 views

### Stability analysis - 0 dB crossover point

I have a question about Bode diagrams. For example if a Bode plot (gain) cross 2 time the 0 dB axis which point should we consider. Should we analyse both of them and keep them stable (good phase and ...
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### Plotting the bode plot of a high pass filter using matlab

I am trying to theoretically find the frequency response of the circuit given below: Firstly i found the impedance value of the RC Ladder by applying the equation below, then i defined this as "...
335 views

### What does Gain mean when LTSpice plots Gain vs Frequency in AC analysis?

I am trying to simulate the frequency response of a trans-impedance amplifier in LTspice, with a current source input, as shown below: My question is when doing ac analysis, the gain that LTspice ...
336 views

### Bode criterion for stability - applicability conditions

While checking Bode criterion for stability, I found several sources disagreeing on what is needed to be able to use it. In general, every source I checked agrees that the open-loop system must be ...
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### What is minimum gain crossover frequency in bode analysis?

I know gain crossover frequency at which magnitude of open loop transfer function is 0. But what is the case here for minimum Wgc?
282 views

### Open loop gain of Op Amp 20 dB lower

I need some clarification regarding the open loop gain of Op Amp. I tried simulating this active BPF on LTspice. The Avol of the Op Amp U6 (UniversalOpamp) is 1meg and its GBW is 10meg. My ...
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### LTspice Bode plot filter analysis

I am designing a π-type LC filter with a frequency cutoff of approximately 1khz. Simulating the filter in LTspice gives the following Bode plot. It starts dropping off at ~100hz before dropping ...
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### What is the negative omega squared in this function?

I'm trying to draw a Bode plot for the transfer function, but I am confused on what the negative omega squared is supposed to be. Is it supposed to be the frequency with no phase angle? How can I get ...
71 views

### How to compensate this circuit? [closed]

I'm using the circuit above to control the common-mode voltage of the 2 resistors. M16 is a current source. The OpAmp controls common-mode voltage by adjusting the resistance of M20. I need to adjust ...
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113 views

### Stability issue: Compensation changes using Bode plot in LTspice

I am encountering issues with a LT8390 design, particularly in higher load current conditions, which leads me to suspect a stability problem. The design parameters are as follows: vin 18-36 (28v ...
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### Bode plot of a boost converter on LTspice

I'm currently learning about controller of boost converter. I tried simulating an LT3580 boost converter (5-12V) based on its datasheet below. What I did was basically copying the circuit from figure ...
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1 vote
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### Why a series resistor on the output of an op amp would add a zero

Capacitance on the output of an op amp I was looking at this post and I totally understand except the answer said that the series resistance at the output of the op amp is creating a pole and a zero. ...
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### 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(...
63 views

### Is there a correlation between conditionally stable systems and non-minimum phase systems?

I know bode plots cannot be used for non-minimum phase systems ( eg: delay, Boost converters). Can we identify the closed loop conditional stability from open-loop bode plot response? Conditional ...
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### 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 ...
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### 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 ...
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158 views

### Frequency response measurement of power converter - Why is the injection point across the resistor?

The standard procedure of measuring the frequency response of a buck converter is to inject a small voltage across a small resistor Rt as shown below. (Ref @4:40) Why do we apply the input voltage ...
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155 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 ...
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