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0answers
51 views

What can I do for this glucose meter circuit?

simulate this circuit – Schematic created using CircuitLab Hi guys! I am making a two-cell glucose meter. Here is may design. Of course, as you see, there are many problems that I cannot figure ...
1
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0answers
56 views

Limiting Output Voltage of the Opamp-to avoid saturation

Problem: my photo diode recieves pulses of width 10ns-150ns and repeating at rate of 1Hz-50KHz the current from photo diode depending on incident light can go from 10nA-100mA, in a nutshell, my ...
0
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1answer
31 views

Why non repeated poles at imaginary axis makes LTI system marginally stable?

I understand that stability for an LTI system is defined with respect to Bounded input bounded output condition. However I'm not clear on why non repeated poles on the imaginary axis makes the system ...
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1answer
24 views

Stray Input Capacltance Compensatlon with constant-GBP OpAmp

In the book: Design with operational amplifiers and analog integrated circuits, section 8.2, it shows a circuit as below: And give: $$f_{z} = \frac{1}{2\pi(R_{1}||R_{2})(C_{n}+C_{f})},\:f_{p}=\...
4
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2answers
82 views

Diode Clamp failing with LDO Circuit

I'm back with yet another mystery. Summary question: Why would an input to a voltage clamped circuit de-stabilize and or elevate that voltage clamp's upper rail? How do you properly clamp voltage ...
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2answers
590 views

Phase Margin Criterion

Why is 45 degrees considered minimum phase margin. Is it just for stability considerations or some other reasons too? Thanks.
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3answers
7k views

Converting and Stabilizing output voltage of a dynamo hub

Preface - I don't know much about electronics :P I have ordered a Shimano dynamo hub for my bicycle. I have done a little homework and here are my findings about it: The output of the above ...
0
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2answers
59 views

Gate driver and instability problem

This is a gate driver circuit for a boost converter. However, there is one part that I don't understand. Could you explain it or give me some links so I can read up about that? Here is the part that ...
0
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1answer
67 views

Build own custom USB 'regulator' adapter board to solve Desktop boot hangs with KVM

My Desktop PC hangs in the BIOS boot phase when my KVM is attached. If I unplug the USB connecting the PC to the KVM, the PC boots without hanging. If the USB of the PC is connected directly to the ...
0
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1answer
68 views

Two DC DC converter with different output - In series or parallel?

Source: LiPo Battery (13V - 16.8V) Consumer #1: 5V (RaspPi) ~1A Consumer #2: 12V (variouse) 0-3A (plus ~1A if series) DC/DC step down: two LM2596 Which would be the better solution: LM2596 #1 on ...
0
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1answer
48 views

Stability of closed-loop systems at -180 degree frequency

Say e(t) is sine wave and y(t) is sine output. If y(t) has the same frequency as e(t) with phase shift of 180 degrees, we can only get stability of the system, if the gain of open loop at this ...
1
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1answer
75 views

Stabilising a constant current load opamp feedback loop

I designed a constant current load around the ACS712 Hall-effect current sensor (module from eBay). This module gives a voltage output of 185mV/A superimposed on VCC/2. Its current range is +-5A altho ...
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1answer
134 views

Meaning of zeros in transfer function

Can someone please explain, provide a link or cite a book where the properties of the zeros for continuous and discrete time systems are explained? I know that the zeros are the frequencies where the ...
1
vote
1answer
108 views

Feedback loop-gain(beta) derivation for the inverting amplifier?

During my study on the negetive feedback concept, i observed that the beta derivation for the non-inverting amplifier is so evident which is just a potential divider voltage.But i am unable to find ...
0
votes
1answer
52 views

How does a magnetic ballast (large inductor) stabilize a negative resistive circuit (such as a fluorescent light)?

When reading about fluorescent lights, I noted many sources stating that a large inductor (the magnetic ballast) in series with a negative resistor (the light, in this case) will stabilize it by ...
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3answers
66 views

Negative feedback - equilibrium

I have a basic question regarding negative feedback and stability. As I've understood it, negative feedback is supposed to promote equilibrium. But suppose we have negative feedback loop block ...
2
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1answer
71 views

Open loop oscillating

Will an open loop op amp with negative phase margin oscillate? I understand phase margin is defined in closed loop transfer function with equating denominator to zero . But will an insufficient ...
0
votes
1answer
26 views

PSU Stability Measurement

The mathematics behind stability are crystal clear. I am very confused, however, as to how these measurements are taken in a real system. Specifically, say I have a power supply. How would one measure ...
3
votes
3answers
212 views

Can a 7805 ever oscillate?

I see many references to input and output caps helping with "stability" and some outright references to preventing oscillation in both answers on this site, and even in some data sheets. I also have ...
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4answers
20k 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 resistors ...
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2answers
73 views

How do I calculate phase margin for a feedback amplifier

I'm learning analog design and can't seem to get a firm grasp on the concept of phase margin and wanted to ask a few questons: First Part: I understand that Phase margin is the difference between ...
1
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3answers
108 views

Delay and Stablity in Negative Feedback Systems: Confusion-2

This question is in reference to my earlier question: Delay and Stablity in Negative Feedback Systems: Confusion In that question I wanted to ask why the second order system is always stable. But I ...
3
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2answers
139 views

Delay and Stablity in Negative Feedback Systems: Confusion

Below is a block diagram that shows an op-amp in negative feedback with feedback network made from resistive divider: The encircled block is Op-Amp with 1 and 2 as its inverting and non-inverting ...
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1answer
51 views

Amplifier with two-pole is unconditionally stable

This is from a lecture slide: Amplifier with a single-pole is unconditionally stable. Amplifier with two-pole is also unconditionally stable. Are these properties considered for closed-...
3
votes
3answers
239 views

Phase margin analysis of a [diy] PMOS LDO [with LTspice]

I'm somewhat familiar with using LTspice to do phase margin analysis for a classic i.e. obvious negative feedback path opamp circuit; in fact I've done that analysis successfully for fixing real opamp ...
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6answers
10k 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) ...
0
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5answers
465 views

Using more than one voltage regulator in series

Is there any problem (in addition to a likely loss of current) in using more than one voltage regulator (L7812CV) in series? And is there a real gain in stability? I ask this because I 'm going to ...
3
votes
2answers
141 views

Systems stability with zero poles

I have a rather simple question I would say. I know that systems having real poles to the right side of the plane will inevitably be instable (for LTI systems at least). But I'm confused with ...
2
votes
1answer
155 views

Unstable points in a basic memoryless circuit

I have been told that there can be more than a single solution to a circuit, and that some of those solutions might be unstable. As a simple example, a resistor with a constant power source, connected ...
0
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1answer
98 views

Step response of feedback system

We have a feedback system F(s) as in this figure: and this is the step response of G(s): and H=10. F(s): We got the root locus of the system F(s) as this: then we determined the gain ...
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4answers
1k views

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 ...
3
votes
3answers
549 views

Can there be “too much” capacitance on a buck regulator output?

I've an MPM3610 buck regulator module with an integrated inductor of 0.47 µH and a fixed internal compensation. It employs constant-on-time regulation. The datasheet gives some application ...
0
votes
1answer
60 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 (...
3
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2answers
184 views

Why do we take gain and phase margin from these points in stability?

In the following graph, why do we take the phase margin from -180 degrees and the gain margin from 0 dB in stability?
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2answers
72 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 ...
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2answers
700 views

Why are low-dropout (LDO) voltage regulators unstable?

LDO regulators based on P-type transistors seem to be the preferred form of linear voltage regulator today, but I keep hearing about how I have to choose the output capacitor(s) carefully to guarantee ...
1
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1answer
40 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 ...
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4answers
7k 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
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1answer
48 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 ...
3
votes
3answers
307 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
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1answer
120 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
100 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 ...
2
votes
2answers
111 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 ...
2
votes
3answers
610 views

What does it mean for amplifiers to be stable only down to N gain, where N > unity?

This is related to What's special about "unity-gain stable"? which is about unity gain stability. But what exactly does it mean if some op-amp is said to be only stable to, say, gain ...
57
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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
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1answer
119 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 ...
3
votes
2answers
502 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 ...
3
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3answers
1k 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 ...
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2answers
614 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: $$ \frac{KG(s)...
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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 ...