Questions tagged [stability]
The ability of an electrical circuit to stop oscillating within a finite period of time. Related topics include the Nyquist stability criterion (and the associated Nyquist plot), Bode plots, and gain and phase margin.
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What do the poles and zeros of a system physically represent?
I've been working with transfer functions and control models for a while, but I never really have gotten an intuitive understanding of what the poles and zeros of a system really represent.
I was ...
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How to regulate a Li-ion battery voltage to a constant 12 V?
I don't know if it even makes sense to regulate a 12 V that's supplied to an 100 0W inverter via lithium-ion battery pack because I need the voltage to be stable even when the battery voltage starts ...
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Differential Amplifier's Unusual Behavior
This circuit is made of one differential BJT transistor pair and voltage-amplification stage with negative feedback.
simulate this circuit – Schematic created using CircuitLab
About this ...
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Barkhausen Stability Criterion and when feedback can be considered positive
My analog design book says the following:
"As a signal \$ S_\epsilon \$ propagates around the loop and returns to the summer \$ \Sigma \$ as \$ S_f \$, it experiences a frequency-dependent phase ...
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Relationship between switching frequency and controller's crossover frequency in DC-DC converters
I am reading some answers related to my questions based on control loop stability of SMPS.
I came across this question.
The accepted answer states:
A switch mode power supply is essentially a ...
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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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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 ...
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How to check for stability for non-constant controller using Nyquist plots?
Let's say I have a unitary feedback system with one unstable (RHP) pole. Now if my \$G_c\$ is a constant, say \$K\$, I know that in order to have stability I should have a single counterclockwise ...
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Constant DC load stability and bandwidth slewrate
For this circuit, how do I know if the rise edge was limited by slew rate or bandwidth? What's the effect of R2 and C2 on bandwidth?
-3db of this circuit in simulation is 649 kHz, I know in this ...
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Latch is stable with competing capacitors?
I inherited the attached design as part of a work project. This is a latch which is meant to hold the high-voltage side of the system in the powered on state when a momentary power button attached to ...
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Measuring oscillator stability vs temperature
How do people measure frequency stability vs temperature? Is it by having the data of frequency vs temperature and then try to fit the curve and finding the temperature coefficient or by finding ((d(...
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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(...
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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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Is it ok to clip component leads after soldering?
When working with through the hole components, I have read that you should clip leads before soldering so the shock from clipping doesn't break the joint. On the other hand I've seen a ton of ...
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Why should 180 degrees of phase margin 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 at 61 to 299 degrees, the output is larger. Shouldn't we consider an ...
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loop gain, open loop gain of op amp in inverting configuration (feedback capacitor)
I was trying to understand the 2nd answer from this post here, with the circuit of the post shown below. The 2nd answer has equations including open loop gain I wasn't able to understand (1st ...
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What does the root locus tell us exactly?
More specifically what information can one extract from a root locus drawing without calculating the transfer function and then using Routh Hurwitz or other techniques? Essentially, what information ...
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Is there any significance of RHP zeroes on a system's open loop behavior?
In a closed loop boost converter, RHP zeroes will cause a phenomenon called ‘non-minimum phase’, which will make the closed loop system go in the opposite direction first when an external excitation ...
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How to get rid of glitch?
I have designed simple P-channel MOSFET circuit. It works well, but when low source power is applied (1 V), a glitch occurs in the output signal.
I tried R, L and C component, but it didn't work.
What ...
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Switching frequency and controller's crossover frequency in DC-DC converters
In the context of control loop stability of DC-DC Converters,
A switch mode power supply is essentially a sampled-data system, therefore the theoretical maximum bandwidth is one half the switching ...
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RC oscillator loop stability with AGC
I am trying to design a sine wave oscillator. The frequency is about 10 kHz (not critical), the distortion should be reasonable but not necessarily super good (say under 1%). However, the amplitude ...
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Optimum phase margin Controller Design
I am designing a PI voltage and current Controller (Cascaded Control for Buck Converter with LC filter) and I am confused about what is the perfect phase margin to choose for the application.
I read ...
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Stability analysis of cross-coupled amplifier in Cadence
I am trying to implement a cross coupled amplifier with OP-AMP feedback.
I am not able to get it stable for a square wave however.
The circuit looks as follows:
The OP AMP is ideal from Cadence, all ...
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Is a fast op-amp more difficult to stabilize than a slow one?
Suppose I want to make a simple non-inverting amplifier with a bandwidth sufficiently low.
Is it harder to make a stable non-inverting amplifier with a fast op-amp? When I read some documentation on ...
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How to stabilize an op-amp with a MOSFET in the feedback loop
I am modifying a current source/sink and there are three circuits that are relevant which are shown below, all using a MOSFET and an op-amp to stabilize a voltage across a sense resistor. My questions ...
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Is it possible to stabilize every system with an integrator
I was wondering if it was possible to stabilize every system with an integrator. From my point of view, an integrator can be used for applying a dominant pole strategy.
If I place the pole at very low ...
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How to evaluate the stability of a full wave precision rectifier
I made a simulation of a full wave precision rectifier but I have some difficulties to evaluate its stability.
I would like to evaluate it stability by a Bode plot because it seems that if the input ...
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How to find gain and phase crossover from a Nyquist plot?
Note: I need to do this by hand which is why I'm struggling. I'm only using MATLAB here to show the nyquist plot, and I was also using it to try and check my answer.
Edit: There are poles at -50, -10 ...
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Op amp stability consideration
I would like to have your opinion on this circuit :
The source voltage V12 is a feedback of an other loop hidden. So the operating point of the system is changing.
When the 47 Ohm resistor R1 is ...
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Fixing Instability in a 5 W Audio Amplifier Board
My prototype 5 W audio amp board based around a (pulled) Rohm BA532 amplifier IC (datasheet) worked just fine. It was built on a section of strip board and was based on the following schematic:
This ...
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Effect of source/input impedance on LDO regulator stability
The datasheet for the MCP1700 family of LDO voltage regulators, in section 5.1 (p.13) states:
...As with all LDO circuits, a relatively low source impedance (10\$\Omega\$) is needed to prevent the ...
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Photodiode circuit to compensate for LED temperature drift
I'm trying to create a stable light source using 5000K white LEDs. In researching this I've discovered that LEDs drift with temperature by a non-negligible amount. Further research leads me to believe ...
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Transimpedance amplifier calculating feedback capacitor
What is the correct way to calculate \$C_F\$ of the transimpedance amplifier? Since I have seen two different documents, and each has a different way to calculate it.
These two documents are:
Akshay ...
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When does the transistor reach the stable status when I add resistor to the emitter
simulate this circuit – Schematic created using CircuitLab
If I add resistor R3, which is an emiter resistor, can it change the value of the base voltage? I've learned that the emmiter voltage ...
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Why do we talk about system stability as a whole when Barkhausen criteria is valid only for one specific frequency?
The relationship AB=1 will be applicable only at a specific frequency. For instance, following is the bode plot for a circuit I have and as can be seen, the barkhausen criterion is met only at 6.3MEG ...
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A question on the response of an RC circuit and pole of its transfer function
Below is an excerpt from an introductory level book about poles and zeros:
The transfer function of the RC circuit system above for the output voltage is:
H(s) = s/(s+10)
The book claims that this ...
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AC analysis of SMPS shows instability. How to modify the analysis to reflect the transient stability?
Background
I have designed a switch-mode power stage with voltage-mode control that uses an LCLC filter in its output to obtain a very low ripple output voltage.
I have empirically arrived at a ...
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Meaning of long term stability unit (µV/mo)
What does 'mo' stand for in a long term stability spec which has units of μV/mo?
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What is actually meant by stability of a control system in practice?
What is actually meant by stability of a control system in practice? I searched many forums but most of them describe stability in terms of equations and definitions, but they don't describe what ...
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How to determine the phase margin when the Bode plot never crosses 0 dB?
I have a graph that looks like this. I am tasked to measure the phase margin, but the graph doesn't exceed 0 dB.
The circuit is this. The input DC level is 0.6 V, which is the problem. When I change ...
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Stability of driven right leg circuit in ECG amplifier
I am currently writing my Bachelor Project about an ECG amplifier. Common mode voltage on the body has a much higher amplitude than an ECG signal. To attenuate common mode noise a differential ...
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If the phase margin stability test fails at a very high frequency that I will never reach, is this an acceptable design?
If I have a system that fails a phase margin stability test at a very high frequency that I will never reach, can we conclude that my system is stable, given that we will never reach the frequency at ...
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Find a point on root locus for specific damping ratio
Although I have seen many types of root locus plots which have some curved behavior, I cannot find the poles for which my system has a given damping ratio of \$ \zeta = 0.59 \$.
I need to somehow find ...
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Isolated Converter - Output Y Caps and Output Voltage Relationship
An isolated switching regulator has 680p/250V Y caps from both positive and negative terminals to the earth, for common-mode noise suppression:
simulate this circuit – Schematic created using ...
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Will there ever come a point where you can take the gain margin using the phase at 0 degrees?
I understand that we use the magnitude at -180 degrees since when k increases, the nyquist plot expands and the frequency that will first touch the pole will be the frequency where the phase is -180 ...
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DC stability issue with this audio amplifier
This design has a stability issue.
The DC output point (without input signal) should be 0 V with a small offset, but it's not the case, because this point is not stable.
Initially the amplifier had an ...
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CS amplifier feedback stability
I playing with JFET Common Source amplifier with feedback loop. I am simulating the design showed here. https://www.ti.com/lit/an/slpa018/slpa018.pdf?ts=1669662908797&ref_url=https%253A%252F%...
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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 ...
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Stability simulation - breaking the loop for a MOSFET - op-amp current source
The task at hand is to create a voltage controlled current source of 60 mA driving a valve coil (64 mH, 139 Ω). I am aware the MOSFET used is insufficient powerwise; it was a quick attempt to have a ...
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