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 happens on a DC-DC grid connection after a perturbation in the synchronous grid?

Consider the Continental Europe synchronous grid. This power system has some DC-DC connections with other countries (for example one with Great-Britain). Suppose now there is a sudden big outage ...
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How are formulas for "in the loop compensation" of capacitive load derived?

I tried to understand https://www.analog.com/media/en/analog-dialogue/volume-38/number-2/articles/techniques-to-avoid-instability-capacitive-loading.pdf The feedback circuit is as follows: so I have ...
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Checking calculation of phase and gain margin in LtSpice

I am currently studying DCDC stability analysis in LtSpice. Could you please check my phase margin calculation, am I right? And how about the gain margin calculation? Is it equal to infinity in my ...
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14-Volt 6-Amp Power Supply Stability

Design Requirements: The purpose is a linear DC power supply for 12-volt aircraft, marine, and amateur radio equipment power source 20 volts @ +/-10%. (output 85W = 6A*14.2V) Rser on V1 = 0.4 or ...
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Why are stability circles circles on a Smith chart?

I am new to basic concepts in amplifier stability, so the question might seem obvious, sorry if it is the case. The amplifier stability translates into the equations for the reflection coefficients ...
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Confused regarding gain margin and stability

I plotted the bode plots of the transfer function: G(s)= 2.123×10^6 ((0.105s+1.01))/(s^2 (s+12566.37) ) It is as follows: As can be seen, it shows the gain margin as negative infinity, however loop ...
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Nyquist plot mirrored across imaginary axis

I am reading Foundations of Oscillator Design by Guillermo Gonzales. When an amplifier is connected in a positive feedback configuration, the transfer function is \$A_{vf}(s)=\frac{A_v(s)}{1-\beta (s)...
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On the stability of differentiator based on OP amp with an example from TI manual

I am building a proportional-Differentiator circuit based non-inverting OP-amp. But I am confused with the stability condition of OP-amp. The system will be unstable if the loop gain |T(s)|=|a(s)B(s)|...
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Stability of dual op-amp Integrator

When we try to analyse the stability of this circuit mentioned here, I find that this circuit is unstable. It has a zero phase margin. I wanted to know how do we stabilise this circuit for practical ...
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Is the power frequency characteristic of a network almost constant?

When a transient phenomenon happens in an electric power grid, the network reacts to this deviation with a power-frequency characteristic (MW/Hz). Reading the following paper ''Analysis and ...
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Does the feedback capacitor in an inverting integrator appear as a capacitive load to the op-amp in an integrator circuit?

In an answer to a question, I was told that the feedback capacitor appears as a load to the op-amp in an inverting integrator topology. If that is the case, we should see a pole with the output ...
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What is the practical advantage of root locus method in control system engineering? [closed]

Recently I learned about the topic. Decades ago, when no computational power was available for engineers, it was surely helpful in some way. But I do not understand what the advantage is nowadays, ...
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Stability/damping of AC->DC PSU with DC output Power Line Filter

Application: I am designing a General Purpose 115V 400Hz VAC->28VDC 500W power supply for powering instrumentation aboard research aircraft. Size < 19" x 2U x 6", weight<10 lbs, so ...
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Nanopower op amp stability

Has anybody got experience of using nanopower op amps e.g. TLV521? This op amp has a very low GBW. In unity gain mode, can a small load capacitor on the output (e.g. few hundred pF) push this op amp ...
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nature of the load connected to the electric power grid

I know that loads can be modeled either as constant impedance or as fixed power P and Q. I also know that the majority of the loads are constant impedance type but I don't know exactly the percentage. ...
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Amplifier Stability - Observing phase margin

I am following a TI lab about opamp stability: "Precision Labs - Op amps: Stability". And I have some trouble to interpret phase margin from bode plot on an example. The transfer function (...
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Relays: What is High Contact Stability?

This TE RF relay datasheet shows the component coming in three varieties: High Dielectric High Contact Stability High Current So high-current is obvious (right?), and (correct me if I'm wrong) high ...
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Why is the phase margin more important than the gain margin?

I heard from some lecturers that the phase margin is more important than the gain margin. However, after searching online and in some control related textbooks I couldn't find any reference for such ...
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Can not simulate stability of op-amp without negative supply rail

I am simply trying to simulate stability of AD8531 op-amp in a buffer configuration. However, when I connect the VSS pin to GND, I have some meaningless result. If the op-amp is fed with at least -...
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5 answers
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What frequency stability crystal do we need?

We're designing a simple digital clock and using a 32.768 kHz crystal with a frequency stability of 20 ppm (standard off-the-shelf SMT). We're finding the clock is running fast by about 2.5 minutes ...
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Instabilities in constant current sources at low load impedances

I want to turn my constant voltage source into a constant current, voltage controlled. For this, I used the following circuit. If the ERV error signal is connected to the UCT, the assembly functions ...
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LDO Outputs wrong voltage

I am working with a very low profile LDO, TCR5RG18A and I'm having issues at the regulators output. It's outputting 0.9V which is half its nominated value (nominal value = 1.8V) The LDO is operated at ...
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How to measure the stability of sine wave peak-to-peak voltage

I am currently using AD9833 to output a sine wave signal. I have seen the sine wave signal on oscilloscope and saved a CSV file on my flash drive. I plan on using an Excel or Matlab to determine the ...
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BIBO and impulsive stability in voltage-controlled electrical circuits

Branching from the comments here, TimWescott gave this example of an open-loop unstable electrical system: Find the nearest NPN power transistor. Put it in a circuit with a healthy (for it) voltage ...
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Open loop system instability

I'm studying system stability, and I know a closed loop system can be unstable due to the feedback. I also know that an open system can be BIBO unstable (e.g., a capacitor with a direct current input)....
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Flyback bode plot & type 2 comp

I'm trying to compensate a flyback boost circuit. Unfortunately I seem to be failing to make the gain of the system ever cross 0 dB. I feel like I'm missing something obvious... Like a pole? I'm ...
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Why is this integrator unstable?

I am trying to convert an acceleration signal to a velocity signal using an integrator. After building the circuit, it turned out to be unstable: With no signal at the input (...
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Is the 'UniversalOpamp2' in LTspice useful for stability in capacitive drive applications?

When using a level 2 UniversalOpamp in a unity gain capacitive drive follower application, I find that it is quite stable. I decided to compare the results to an actual opamp model of the LM7321. I ...
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What is the better way to stabilize this discrete op-amp and why?

I have the following simple op-amp circuit, which is meant to drive a MOSFET (M1) gate and work as a voltage regulator. It is discrete for a mix of reasons (necessary bandwidth, using existing BOM ...
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BIBO stability on a accumulator system from oppenheimer book

Is this stability correct?. If im getting it right, x[k] has a bounded value(M), so the interval between the summatory times this value tells the max value of output. But shouldn't it be |n - no + 1|M?...
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How to set up an LTSPICE test bench for Common Mode Feedback Loop Stability

Suppose we are given a fully differential (low voltage single supply) op amp with common mode feedback. It is common knowledge to break the loop in order to measure open loop ac performance for loop ...
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Why is my voltage pulsing when using a DAC as an input to an OTA?

I'm using the LM13700 in an automatic gain control configuration to adjust the volume of a speaker based on the audio level perceived by the microphone. Both amplifiers on the chip are used: one to ...
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Ideal OpAmp differentiator stability

So, for OpAmp stability, we don't want \$A_{OL}\beta\$ to be -1, which we can derive from the Bode plot by looking at: \$20\log(A_{OL})-20\log(1/\beta)\$ and looking at the rate of closure to indicate ...
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Disadvantage of 3rd order vs 2nd order digital PLL with high C/N0?

I tried to determine the best choice between an aided 2nd order and an unaided 3rd order carrier digital PLL in a context where the \$C/N_0\$ is very high. From all aspects, the 3rd order loop seems ...
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Problem stabilizing this PMOS LDO

I am considering a discrete LDO for a supply rail that needs ~\$m\Omega\$ impedance at 10 kHz. While the following circuit does what I need (according to Spice), it becomes unstable if C2 is smaller ...
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Why does Nyquist plot show no encirclement when positive feedback is unstable?

Amended the previous question to be more concise I have the following open-loop plant: $$G(s)=\frac{21.95s^2+224.2s+1906}{s^4+32.7s^3+285.8s^2}$$ These are the poles of the plant, and as you can see, ...
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Flyback power supply instability issue

I have created a switching power supply: Input: 230 V AC Output: 12 V DC, 1 A Controller: UC3844 Topology: flyback Switching frequency: ~ 100 kHz Schematic: When I start this power supply, output ...
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What happen if one connects two live phases together? [closed]

If a house is running on 1 phase wire and is flipping instantly or not stable for a short period as it drops from 200v to 170v and return back to 200v in 10 seconds. Would connecting another phase to ...
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Why does the rotor magnetic field lag the rotor current by 90° in a 3 phase induction motor?

I was trying to understand load angle in electrical machines, generally denoted by delta, and I found out that while delta needs to be less than 90° in synchronous machine for steady state stability, ...
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IGBT Temperature Drift: How to Achive Stability?

I remember the BJT transistor circuits are designed to compensate for the fact that the parameters of the transistor change with the temperature. I could not find similar ready-to-use solutions for ...
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Why does this oscillator not work with a voltage less than 9 V?

By chance of my research and simulations and various tests, I found the diagram of an oscillator with strange behavior. All the oscillators (quasi) that I have encountered work whatever the supply ...
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Why does this PMOS LDO require no compensation to be stable?

LDOs with PMOS pass transistors are prone to oscillation due to positive feedback problems as discussed e.g. here. Now the below simple circuit is basically a PMOS LDO, but seems stable in both time ...
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Please help me clear up this confusion regarding gain margin and phase margin and unity feedback

I understand the physical significance of gain and phase margin. However, I would like some clarification regarding the mathematical aspects. Videos such as the following: https://www.youtube.com/...
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Voltage regulator stability, PMOS v NMOS pass transistor

Currently, I am considering some LDO replacement circuits because some parts have bad availability. For small current demands (up to maybe 20 mA) I think, a simple opamp will do fine, but for larger ...
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Stability problem when using an OpAmp to drive a BJT for high current application

I am designing a circuit for my lab, and in that application I need to have several low noise current source driving coils at roughly 7V, 20A. I could not find a benchtop power supply cheap enough so ...
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Phase lower than -180 when reaching unity gain, is it unstable or can we substract 360?

I am getting a phase of -434 degrees when reaching unity gain (0 dB point). The phase curve starts at 0 degrees, thus, can we consider that -434= -434+360= -74 degrees and the phase margin is of 180-...
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Caveats of the RC phase shift oscillator

I was reading some articles online where it talked about this kind of RC oscillator. I just want to clarify some caveats about this circuit: From: https://learnabout-electronics.org/Oscillators/osc31....
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Understanding on frequency compensation on driving capacitive loads with an op-amp

I am trying to understand an example circuit of frequency compensation on driving capacitive loads with an op-amp from: https://www.allaboutcircuits.com/technical-articles/how-to-drive-large-...
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Reduce hard voltage drops on mains? [closed]

I'm experiencing some hard voltage drops on my AC power line (measured at 20 points across the house). The culprits are the washing machine and dryer (as well as our upstairs neighbors washer and ...
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Are there common circuit stability issues at low current levels and/or recommended minimum values?

I'm building a small semi-permanent solderable PCB circuit using a couple of mosfet inverters, plus some resistors for voltage division and pulling inputs/outputs high/low. The final location will be ...
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