Questions tagged [stability]

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Control Loop Stability - Crossover frequency

I am testing the control loop stability of a DC-DC Converter. One of the Pass-criteria of the DC-DC Converter states, "Cross over frequency should not be higher than 1/8th of switching frequency" ...
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Why does continued fraction expansion work? [migrated]

While checking whether the given polynomial is Hurwitz or not, we perform continued fraction expansion. We were taught how to perform this check(i.e) look at the sign of the coefficients of the ...
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What is the Rseen from this node?

In the text book I am reading (CMOS Analog Circuit Design by Razavi) the author wrote that the Rseen from node N is (1/gm7), however when I derived it myself I found that the Rseen is ro4 // ro6 (...
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Question about feedback in a current reference

I'm studying the following Vbe-based current reference: The author of my book says: Observe that the circuit has two feedback paths around the gain stage. One positive, the other negative. ...
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Unstability condition for positive feedback network involving phase change

For positive feedback: $G=\frac{A}{1-AB}$ According to Wikipedia, this system is unstable for AB>1. This condition appears to be for the cases when 'A' and 'B' have real values. But in general, A ...
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Gain margin using Root locus plot

How can I find Gain margin of any control system given its polar plot In schaum's series I have read that Gain Margin=Ku/Ki but in given figure the system never becomes unstable so shouldn't Gain ...
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Opamp isolation resistor calculations for a capacitive load

I want to add a capacitive filter for pulse shaping to the output of a transimpedance amplifier using an OPA847. Without the filter, the amplifier works great. With the filter, I get some ...
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Abuse TS339 comparator channel as a voltage multiplier

I have multiple free channels of a TS339 amplifier remaining and would like to use one of them to multiply voltages like this: simulate this circuit – Schematic created using CircuitLab Now it'...
45 views

MOSFET Capacitance clarification

2 part question here. Are there ways to directly test the input and output capacitance of a MOSFET, Ciss and Coss? On that note, due to internal inductance and capacitance, is it possible for a ...
30 views

Phase margin Vs damping ratio: Intutive explanation

While designing the compensator for SMPS we always talk about the relation between phase margin and damping factor( or Quality factor). I don't completely understand how damping plays such a keyrole ...
57 views

Stability and Positive/Negative feedback

I often read that positive feedback is used to get oscillators (since the output of the circuit is summed up to its input signal and so leads to instability), while negative feedback to get amplifiers ...
54 views

Understanding a ZVS Oscillator in-depth

For a project I've been building, I've been using the (overused) ZVS oscillator that can be found online. So far it's been working great transferring power wirelessly, but I'm interested in ...
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Stability of Buck Converter when output capacitance is variable

I am designing a buck converter for an application that has several different loads. Depending on what devices are connected, the capacitance seen at the output of the buck converter can vary ...
102 views

Bandwidth and stability of nonlinear circuit

I'm designing an antilog amplifier which produces an exponential output (0.4 mV to 4 V) for a 50 Hz sawtooth input waveform (4 mV to 4 V ramp). If this were a linear circuit, I could determine the ...
105 views

LED brightness stability issues - how to fix?

I am performing an imaging experiment in which LED stability is critical. I use 2-3 red LEDs to illuminate a surface while imaging that surface. In each LED circuit, I use a constant-voltage ...
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Negative feedback and op-amp poles

I'm trying to get a better understanding of frequency compensation for op-amps. I'll start off with a very specific questions and then get into the context. For a certain op-amp, open loop gain is ...
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Could i get some circuit design feedback?

I have a computer science background and this is the first circuit I've ever designed. It is a lot of fun designing these circuits, but it also always feels like I'm missing a lot of "obvious" common ...
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Voltage regulator feedback circuit and stability analysis?

I have been analyzing following buck-regulator circuit to calculate the phase-margin and gain-margin. Circuit Diagram: Buck regulator with input voltage = 12 V and output voltage = 3.3 V. Just as ...
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What is the importance of Lyapunov stability for non linear control?

I understand that studying stability gives a particular region from which if we start it will converge to an equilibrium point. But why is the study important specifically for designing non linear ...
349 views

Opamp stability given in not inverting configuration

If a datasheet (like AD828) says that an opamp is stable at Gain >2 (or reccomends to work with G>2, hence it is clearly not unity gain stable), what can we deduct about its stability in the inverting ...
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Stability Current Sink

I’m currently trying to create a programmable current sink. And I’m still trying to build up my circuit and searching for new parts. As I was searching for a OPA, I encountered much information about ...
306 views

Effect of RHP zeros on stability

Why do zeros in the right half of the $s$ plane reduce stability (i.e., gain / phase margin)?
105 views

Stabilize circuit on 5V 2A

I have not yet build following circuit: Circuit in high performance needs 5V 1.7A (measured). I have source which is powerbank with 16 000 mAh. Outputting via ports: USB-C 5V/3A, USB-A 5V/3A, Micro-...
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Why does music synthesizer built from chain of astable multivibrator circuits get “out-of-tune” after a few hours?

I built a prototype keyboard/sound synthesizer using a chain of 13 astable multivibrator circuits whose outputs are connected to an audio amplifier chip (LM386) and speaker, all powered off a 9V DC ...
38 views

Stability Criteria of Type 3 Digital PLL

I suppose we can derive the stability criteria based on poles of open-loop transfer function of F(z) in expression (4.11). However, the pole analysis does not help in deriving the stability criteria ...
104 views

Is this mosfet stable? Trouble with capacitances

I have the following circuit and I'd like to know about its stability : From what I've learned from basic electronics courses, the first step is to add the parasitic capacitances. I know there is ...
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Questions about stability circle and impedance matching

I'm a RF circuit beginner and got stuck in stability related issues. According to Pozar's textbook, output stability circle is a contour in the "gamma_L" plane and its arc represents the "gamma_L" ...
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Does the stability of an LTI system depend on the input?

Consider a system $G(s) = \frac{1}{s}$. It is marginally stable, as it has its only pole at $s=0$. However, if we apply a step input, the output is $tu(t)$, which turns out to be unstable. ...
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Understanding Optimization/Realization of the voltage controlled current source

I am unable to make a voltage controlled constant current source. So I am using the following scheme (Sorry for bad sketch drawing): The constant control voltage varies in the range of 0 to 5 V is ...
272 views

Stability at loop gain <1 and 180 degree phase shift

I'm reading this article about stability of OpAmps: Link to article. It says: "If Aβ is less than unity at the high frequencies where phase shift reaches 180°, the high-frequency phase-shifted ...
104 views

According to the Nyquist criterion this system is stable but when I apply an impulse I get an unstable response, why?

I have this open loop transfer function and I have to study the stability of the closed loop transfer function using the Nyquist criterion. What I got is that the characteristic equation 1+GH(s)=0 has ...
82 views

Series voltage reference unstable with a series resistor

I am using the MAX6035 as a 5V reference that draws 5mA load current. To protect the input from transient spikes, I thought a simple resistor and zener diode circuit would work well. I noticed that ...
88 views

Nyquist Stability Criteria

Find the stability where: Find the stability: $G(s)= \frac{(s+3)(s+5)}{(s-2)(s-4)};$ $H(s)= 1;$ I run this code in matlab: ...
92 views

How does transistor bandwidth affect stability?

I was watching a video where Dave Jones of EEVBlog interviews Rod Elliot of Elliot Sound Products. Rod was discussing that he tends not to use digital chips in his designs because the chip will become ...
87 views

induction motor stability

Does the change in slip (s) have any impact on load torque in an induction machine/motor? I know it affects the motoring torque. But do the load torque also get affected by the slightest measures if ...
58 views

Derivation of stability criterion for type 3 digital PLL

Could anyone help to derive the following expression (4.23) which is the stability criterion for type 3 digital PLL ? Note: Screenshots are taken from Floyd Gardner's book : Phaselock Techniques 3rd ...
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Cap maximum wall outlet voltage

I live in a rural area. A problem occured when my UPS could not run my computer simply because of voltage fluctuations. I have tried many stabilizers but its too rapid that it would make a tick and ...
107 views

Determine the value of a constant for which the system is marginally stable

So I have the following transfer function $$G(s)=\frac{s^2+0.1s}{10s^3 + 1.1s^2 + 0.01s + 2K}$$ Now I'm trying to determine the value of K so that I have a marginally stable system. I'm not supposed ...
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Non-inverting op-amp configuration with capacitor

I don't really get what is the purpose of the capacitor C1 which is connected in parallel with the feedback resistor. After my knowledge, if we modify the input signal frequency the over all gain will ...
117 views

LT spice not predicting instability

I'm trying to make a linear regulator using an op amp and a pass transistor. Here is the circuit: From my limited understanding you can predict the stability of the circuit's feedback loop by ...
761 views

Op amp driving a LED oscillates, how to stabilize?

I have a simple LED driver circuit like this: simulate this circuit – Schematic created using CircuitLab The op-amp is OPA354 250-MHz, Rail-to-Rail I/O, CMOS Operational Amplifier supplied ...
I learned in basic control theory that we can determine the stability of an LTI system by the signs of the real part of the poles of its transfer function $H(s)=\frac{N(s)}{D(s)}$. For a rational ...