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6
votes
4answers
240 views

Gain margin and Phase Margin Physical Meaning

I have been trying to understand the physical concept of Gain and Phase Margin.From what I understand it a relative comparison around the critical point (-1,0) which when converted to magnitude and ...
1
vote
1answer
36 views

phase-stability two op-amps

I'm trying to simulate two op-amps back-to-back (G=30 each) in LTSpice and work out if they will be stable. If I look at the .ac analysis after the fist op-amp I have good phase margin (about 60 ...
0
votes
0answers
32 views

How to choose output network RC and RL values of an audio amplifier?

With "output network" I'm referring to that RC series circuit connected from the amplifier output to the ground, and the following RL parallel circuit connected in series with the output. I know what ...
0
votes
2answers
51 views

Control: what is the proper justification that you can't just make the output equal to the input if the system produces unstable output

Suppose we have a signal, it goes into the plant and generates an unstable response, a common question then arise at that point is why can't we just set our output to a "hard-coded" input. Think of ...
2
votes
3answers
115 views

Why 60% overshoot with 55° phase margin?

UPDATE: Based on the answers I received, I got this working beautifully. There's a full outcome report in one of the answers below. I'm working through the design of an electronic load, basically a ...
1
vote
1answer
68 views

Why does smaller step show instability better?

I was stability testing a simple op amp circuit by applying a square wave to the input and looking for ringing etc. on the transitions. I figured, hey, I'll give it a big whack, say from 0 to 5V, ...
2
votes
3answers
71 views

How do I determine \$R_o\$ for an op amp?

I understand that when driving a capacitive load with an op amp, the output resistance, \$R_o\$, of the op amp interacts with the load capacitor to form a low-pass filter, introducing a pole in the ...
0
votes
1answer
34 views

Stabilize a 12V DC supply (from Lipo)

I'm newbie in electronics, but I want to learn some basics things. I have a 12V DC output (from a charging/discharging PCB Lipo battery), and I would like to stabilize it to run a mini-amplifier ...
0
votes
0answers
70 views

Is it possible to describe an unstable circuit in VHDL?

i was reading this (VHDL: Signal assignment question) post and i got curious about an issue that i wander if it could arise writing VHDL code. Is it possible to write the code for an unstable ...
2
votes
2answers
59 views

What can be inferred from the frequency an op-amp is oscillating at?

For whatever reason, I seem to create a lot of oscillators in the course of developing circuits involving op-amps. I'm wondering if the frequency of oscillation, which normally appears to be quite ...
55
votes
7answers
4k views

Why is my circuit so incredibly sensitive to electric fluctuation?

I recently finished building a circuit showcased in a beginner’s electronics book. I have included the picture of my creation below because I think it may become relevant to the question. At the ...
1
vote
1answer
69 views

Step-down converter and ceramic minimum ESR capacitor

I'm building a step-down converter, based on the TI TPS5450, which provides a reference design and various considerations on the capacitor. Even on the minimum ESR required. But when states "The ...
0
votes
1answer
25 views

Explanation for stability criterium microwave amplifiers

Given a general microwave amplifier circuit For this amplifier (transistor) to be stable the the magnitude of the input and output reflection coefficient must be smaller than 1. But why? What is ...
3
votes
2answers
125 views

Alternative ways to maintain temperature stability of silicon BJT circuits other than feedback resistors

So I've been messing with Bipolar Junction transistors lately and I'm trying to really nail the concepts of designing circuits with these things cause I want to start using them in some of my circuits ...
0
votes
2answers
110 views

Phase Margin Criterion

Why is 45 degrees considered minimum phase margin. Is it just for stability considerations or some other reasons too? Thanks.
3
votes
3answers
246 views

Why is my op-amp oscillating?

I am attempting to build the following circuit using an LM6171 op-amp. I know that this op-amp is unity-gain stable. I previously had this circuit working with an LT1637 op-amp, but I had to switch ...
0
votes
2answers
286 views

Obtaining stability information from Bode plots

I am trying to understand the theory behind gain and phase margins from Bode Plots for systems with negative feedback, specifically this one: The transfer function for this system is: $$ ...
4
votes
5answers
1k views

What components or circuitry exist that can provide extremely high speed, accurate clocks?

I've been curious for awhile now about doing some high speed projects, such as measuring time differences of radio wave reception, and was wondering if there exists components that provide clocks much ...
-1
votes
2answers
38 views

Feedback Stability Comparison [closed]

Compare the Feedback conditions given below in terms of stability:- Negative Feedback Positive Feedback with LoopGain < 1 Positive Feedback with LoopGain = 1 Positive Feedback with LoopGain > 1 ...
2
votes
1answer
76 views

AP5002 step-down switching regulator loop stability

Problem, parameters I have an 5V output power supply, with 2S LiPo input (6-8.4V), implemented with AP5002 (PWM control 2A step-down switching regulator, docsheet), and for the life of me, I can't ...
0
votes
2answers
76 views

Why would the Schmitt trigger relaxation oscillator a bit unstable?

This thing oscillates from time to time. Why? (Respect part numbers, all chips from NXP) simulate this circuit – Schematic created using CircuitLab ...
0
votes
0answers
96 views

Will this self latching button work without oscillating?

This design is based on EEVblog soft latching button but I am getting inconsistent results from breadboarding. The original EEVblog design oscillates when the button is kept pressed. The original ...
3
votes
1answer
114 views

Effect of zeroes in system stability

Suppose we have two third order systems (a and b), with three poles and two zeroes,poles for both the systems are at the same positions in frequency domain but these systems differ in the placement of ...
1
vote
0answers
79 views

Self-oscillation in a commercial RF amplifier

I purchased several 50 ohm (in/out), 35 dB gain photomultiplier tube (PMT) amplifiers from a vendor assuming I could use them to read out the voltages on my PMTs. The amplifiers are AC coupled with a ...
2
votes
4answers
748 views

Stability and loop gain of negative feedback systems

When we look for stability of a feedback system, why do we only concentrate where loop gain is unity and check the phase margin there. The phase of the closed loop system might be passing through 180 ...
0
votes
3answers
61 views

What things to think about when selecting a relay for controlling small valves?

We are creating a novelty drink dispenser that controls a set of 8 pumps with a Siemens Simatic Step7 1200 PLC. The decision to use this PLC was based on our need to have a very stable prototype. Now ...
1
vote
0answers
169 views

LDO Regulator Overshoot

I'm using an LP38691 3.3V fixed regulator which is overshooting. This wasn't an issue for years, but now a component is being replaced and the current on the 3.3V rail has gone up from 300mA to 500mA. ...
0
votes
1answer
72 views

Powering circuit with alternative and/or concurrent power sources

I have one of these led projectors which is normally powered by the embedded motion sensor. I want to be able to power it manually by a switch button. I need to do this in both alternative and ...
0
votes
0answers
63 views

What could be the potential reasons for an unstable DAC output like this?

I am simply using a DAC and trying to generate a DC voltage with it. However, the output is unstable from time to time, with very strange diagram on the scope. The diagram is as below. Could I ask ...
4
votes
2answers
175 views

Understanding resistors on inputs/outputs of op amps

I was looking at the schematic for Dave Jones' uCurrent, and I can't seem to make sense of why there are 270 ohm resistors on the inputs and outputs of the op amps in his circuit. The resistance is ...
1
vote
1answer
2k views

Where to find derivation of s'' (stability factor for beta) for BJTs?

I'm looking for the derivation of the formula for the stability factor (\$S''\$ or \$S(\beta)\$) of BJT bias circuits, particularly the ones with emitter resistance. The book I'm using says that the ...
5
votes
3answers
715 views

How to know whether the bandpass filter is stable

I am designing a bandpass filter using MFB. However, I do not know whether my filter is stable or not. Can anyone give me some criteria or methods to evaluate the stability of the filter design?(still ...
0
votes
2answers
90 views

Get transfer function from electrical scheme [closed]

Is there any software/SPICE tool in which I can draw electrical circuit and after that, software prints the transfer function in Laplace domain? I will find this kind of tool very helpful and ...
2
votes
3answers
173 views

What is the usefulness of Internal Stability?

In the analysis of a feedback control system is it important that a sub-network be itself stable. i.e. if I were to break apart the main complex system and just study a single feedback loop, is it ...
3
votes
1answer
109 views

Observer Based Control System Design

Consider the discrete-time system described by $$ x(k+1) = \begin{pmatrix}0 & 1 \\ -2 & -3\end{pmatrix}x(k) + \begin{pmatrix}0\\1\end{pmatrix}u(k) $$ a) Find a feedback state vector that ...
1
vote
1answer
52 views

State Feedback Controller

Are there any values of \$\alpha\$ for which it is possible to find a state-feedback gain for the system by bringing all closed-loop poles to zero? If your answer is affirmative, find a feedback ...
2
votes
2answers
254 views

Coil-less AC-DC line regulator

I'm trying to fix an AC-DC line regulator that I have build and doesn't work as expected. I'm trying to convert AC 220V mains to DC 5V 10mA without a transformer. To do this I'm using an 1uF 250VAC ...
0
votes
3answers
191 views

Securing a pcb to be used in a keyboard to its case

I'm looking for a way to secure a pcb I will be making for a cherry mx (homemade) keyboard to a case which I'll also be making. Obviously, I don't want the pcb to move. I could use standoffs/screws, ...
1
vote
4answers
2k views

Powering 28 LEDs in series by 220VAC - simple stabilizer

I have a home-made thingy that I would like to use as a lightning in my living room. It contains 7*4=28 LEDs (red, 1.86V, ...
11
votes
4answers
10k views

Choosing resistor values for non-inverting amplifier and why?

The gain here is A = -Rf/Rin. However, lets say I want a gain of 10 V/V. Which resistor value would you choose and why? I know that you could have infinite number of combinations for these ...
1
vote
0answers
124 views

Forming Nyquist Plot from magnitude and phase transfer function graphs?

So the solution is present above, but I'm having issues understanding the Nyquist Plot. So here's what I know from the magnitude and phase graphs: At \$\omega = 0\$, \$G = |\infty|\$ At \$\omega ...
3
votes
2answers
112 views

Force amplifier into oscillation

The Minicircuits RAM-8+ amplifier has been replaced by the pin compatible RAM-8A+ part. The old RAM-8+ part was conditionally stable and I had to use an extra output attenuator after the amplifier to ...
2
votes
1answer
201 views

Load capacitance estimation for compensation of switching power supplies

I'm calculating a compensation network for power supplies based on the LM20323MH from TI. I have slight doubts about correct estimation of output capacitance to use in the calculation. The board is ...
3
votes
2answers
1k views

How can I stablize an analog to digital reading?

I've built a clock out of a PIC16F877, some LEDs and other stuff... To set the time in 5 minute intervals, I'm using a 22K ohm potentiometer connected between GND and +5V with the contact connected ...
9
votes
4answers
2k views

Conditional stability

I'm learning about op-amps and feedback and how feedback affects their stability. I've been reading about gain and phase margin and their uses when I came across this: I don't quite understand ...
7
votes
5answers
6k views

Stability problem in unity-gain opAmp

As a part of a controlled power supply for hardware-in-loop testing for a student driven project, I had to develop a current buffer (voltage follower) which could source up to 1 A. I had the (bad) ...
5
votes
2answers
608 views

Does MEMS accelerometer stability deteriorate over time?

I am wondering if over time MEMS accelerometer produces any worse output than when it is new? I found this research paper which acknowledges that temperature affect sensor output but there are no ...
2
votes
1answer
285 views

Given bode plot, determine the poles and zeroes

Ultimately, I want to figure out the transfer function $$H(s)$$ But to know that I would need to know where the poles and zeroes are. Looking at this, I know $$ H(20j) = 0 $$ but that's pretty ...
2
votes
1answer
707 views

How can you guarantee stability of an inverting opamp configuration amplifier?

I had to design a circuit for measuring the voltage of a negative power supply rail (-15 V) and feeding it into a ADC (0-3 V DC-coupled input range). This measurement is only used for diagnostics and ...
2
votes
1answer
5k views

Arduino alternate PWM input method

I'm working on a rudimentary flight stabilization system for an airplane, which reads in 4 PWM inputs from an R/C receiver. The problem is, the pulseIn command is taking far too long to execute, so I ...