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 ...
114 views

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 ...
1 vote
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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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1 vote
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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 ...
1 vote
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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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1 vote
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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, ...
71 views

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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387 views

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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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-...
1 vote
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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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