Feedback is a process whereby information from an output of a signal is used (intentionally or unintentionally) to alter the input of the same signal. Commonly used in operational amplifiers. An everyday example is the high-pitched audio frequency heard when a microphone picks up audio from its own ...

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43 views

Why is a 0V DC point at the output of an op amp critical for feedback?

I am designing an op amp that consists of an active loaded single ended output differential amplifier that is connected to a buffer stage and then an output stage. When the input signal is connected ...
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4answers
66 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 ...
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2answers
51 views

What is the correct transfer function of a feedback loop if the summing amplifier has different input resistors?

Suppose I have a circuit below: simulate this circuit – Schematic created using CircuitLab I know the the transfer function of a negative feedback loop is: ...
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2answers
83 views

Why do we compensate PWM controllers?

I have been studying switch mode power supplies for a while. I have understood the working principle of several common topologies But there is a detail in the control circuit structures which I still ...
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3answers
138 views

What is the drawback of a high-value resistor for positive comparator feedback / hysteresis?

I'm building a simple circuit which has an LM211 comparator at its heart. The positive input is connected to a 10k-10k resistor divider across the supplies, stabilized by a 1uF capacitor. Hysteresis ...
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2answers
72 views

Are those two filters equal?

Are those two filters equal to each other in their functionality? Of not, what is the difference between them mathematically speaking (zeros, poles, etc)? Also, what is the difference in their ...
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0answers
171 views

Can I turn an LM2596 switch mode PSU into a constant current source?

I have a cheap LM2596 switch mode regulator from eBay: Which I can power with a dual cell LiIon supply (6 to 8.4V). I would like to use this supply to create a variable current source for an LED ...
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2answers
71 views

Can a combinatorial hardware circuit with no inputs solve a crypto problem?

I am noob at electronics but in short I am interested in stable states of circuit with no inputs which represents a boolean formula. Let \$f\$ be some hash function, say md5. Restrict the size of ...
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1answer
36 views

Help understanding onboard power supply measurement test connections

I recently came across this circuit for measuring the output of a TPS54620 switching regulator (12V->3.3V). I'm not a power engineer, so I'd like some help understanding the parts in red boxes ...
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5answers
332 views

CMOS inverter with feedback

In some circuits such as crystal oscillators, there is a CMOS inverter with a feedback resistor, they all simply say the resistor bias the 'amplifier' and force it to operate in the linear region, ...
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1answer
88 views

How does feedback in power supply work considering output change delay?

I'm designing an SMPS with a PIC microcontroller, but this question applies not only for SMPS but to linear power supply too. I set a desired output voltage in my microntroller and then I perform ...
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1answer
83 views

Alternative LEDs Blinking circuit(Analog) Help

Can someone explain the operation of this circuit, I understand the basics of the BJT and its modes, but most of my confusion arises when there is some-sort of feedback loop in the circuit, my thought ...
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1answer
88 views

Output impedance of current series feedback BJT amplifier?

So according to what I've read, in a common emitter BJT amplifier, an unbypassed emitter resistor acts as a current-series feedback path. The gain without feedback is: ...
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1answer
65 views

How do I use one feedback pin with two error amplifiers?

I know there is a similar question asked: TL494CN and error amplifier. However, that link does not answer my question. If I need one current loop and one voltage loop on the power supply, how should ...
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5answers
178 views

Kinds of Feedback

"Feedback is a process in which information about the past or the present influences the same phenomenon in the present or future" I find the idea of feedback quite fascinating and i could ...
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3answers
103 views

Audio FET Buffers and Negative Feedback

I am struggling to come to term with how negative feedback helps widen the scope of input signals coming into FETs (or OpAmps for that matter, but I am using J201 JFETs). I am aware that the largest ...
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6answers
116 views

What is feedback in electronics? [duplicate]

I dont want to know that we have two types of feedbacks and why it was invented,I just want an explanation in simple words of what feedback is.
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4answers
2k views

How are positive and negative feedback of opamps so different? How to analyse a circuit where both are present?

In an opamp, feedback on the positive input places it in saturation mode and the output is of the same sign as V+ - V-; feedback on the negative input places it in "regulator mode" and ideally Vout is ...
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3answers
95 views

Step response to feedback loop with disturbance

When using step response to a feedback loop with disturbance. Why do we analyze the step response of the disturbance D and the step response of the input R separately. Instead of considering them ...
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1answer
82 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 ...
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1answer
43 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 ...
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3answers
95 views

Inverter Voltage Control - Stability Concerns

I have a voltage inverter that converts a 400VDC source into sine wave of 240VAC @ 50Hz. The inverter is based on a H-Bridge. The inverter works well but I'm struggling in understand how to control ...
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2answers
133 views

Ring oscillator frequency

According to Barkhausen's criteria, for oscillation the feedback should be made after phase difference of 2pi and gain has to be >=1. Now when I consider a ring oscillator if 2 inverters are ...
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2answers
89 views

Why feedback resistance is high?

simulate this circuit – Schematic created using CircuitLab In this drain to gain feedback resistance biasing circuit, it is said that the feedback resistance Rg is large and usually in ...
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3answers
219 views

A few OPAMP questions I have a hard time finding the answers to [closed]

I have a few questions, which, albeit, may seem pretty obvious to a lot of you, but I couldn't find the answers myself, so apologies in advance. Also, the pictures are pretty rough, I know, but that's ...
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3answers
444 views

RC phase shift oscillator : how to give positive feedback?

why is negative feedback given in a rc shift oscillator although a oscillator requires a positive feedback? as shown in this figure. And as shown here positive feedback is given by connecting the ...
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0answers
87 views

How to model Texas Instruments UCC28700?

I'm using Multisim in an attempt to simulate a flyback supply design reference by Texas Instruments that makes use of a voltage controller - the UCC28700. Multisim has no SPICE model natively nor does ...
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2answers
208 views

How to suppress current spikes in transistor feedback loop

I am trying to pulse a load with a small constant current pulse (2mA @ 500us). The load does unfortunately have an unknown capacitance in the range 10nF - 1uF, parallel with an unknown resistance ...
3
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2answers
268 views

BJT cascading amplifier

Im trying to analyze this piece of circuit and the feedback between the second transistors emitter to the base of the first transistor is confusing me. Does anyone have any ideas how to analyze the ...
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1answer
84 views

How can I protect my SMPS feedback voltage divider from loading effects?

Background: I now have a working switched mode boost converter on a breadboard, working as a 12 Volt DC to 24 Volt DC converter. I was troubleshooting what looked like an output voltage problem when I ...
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2answers
89 views

Is an AB amplifier feedback like this (image inside) possible?

Whole question in the title, don't know what more information is possible: Is an AB amplifier feedback like this possible?
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1answer
47 views

Eliminating battery/bluetooth feedback

Let me preface this with saying that I'm a complete amateur with electronics and know very little of theory behind it. I think my question is easily answered but I just can't find the right info. I ...
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1answer
277 views

FM transmitter feedback capacitor [closed]

Why is a capacitor connected across the collector-emitter of the transistor? How does this capacitor prevent decay of LC oscillations?
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4answers
3k 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 ...
3
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2answers
217 views

OP-AMP Positive/Negative Feedback together

I've read several articles about the application of OP-AMP negative feedback. As far as an application for positive feedback, I came across hysteresis and it makes sense. Are other uses for positive ...
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0answers
111 views

PD control (PID without I) - Homework help

I've been given a system - x" = bx′ + kx + ru and I've been asked to rewrite it in the canonical form x' = AX + BU. I've got -- ...
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1answer
101 views

OP-AMPs in a Loop

I am trying to understand what an OP-AMP looping is used for? For example, this is the circuit that I am dealing with: I didn't connect the entire pins, but I hope I made the point accross. I have a ...
0
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1answer
67 views

Inverting OpAmp with reference voltage

Can anyone please explain how to calculate Vout for both cases below? 1 case, simulation shows Vout is -1V 2 case, simulation shows Vout is +2V! I understand how things work when there is a virtual ...
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0answers
81 views

How to deal with unstable pole?

I'm trying to use PD control to keep an inverted pendulum centered, by attractive electromagnets mounted as a radial magnetic bearing. The control is cascaded into an inner current control loop and an ...
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2answers
122 views

Searching for an analog circuit solution, where an output voltage is incremented or decremented based on an input

So I have an interesting request that I've searched the internet for and have not been able to find, or been able to come up with in my head. I have a circuit with a feedback loop that is meant to ...
2
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1answer
154 views

Minimum feedback resistor Rf for given opamp ex: opa2134

i have a problem that needs solving; What is the minimum feedback resistor for modern opamps like opa2134 ? can it be 100 ohm? Im asking because in lt1028 datasheet its says it cant be <100ohm ...
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1answer
285 views

How to identify the feedback topologies?

It is extremely important to identify the feedback topology first before starting analysis. However, I find it difficult and cannot get it right. Is there an accurate yet easy way for me to identify ...
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1answer
106 views

Calculating feedback factor \$V_f/I_o\$

I'm unsure how to calcuate the feedback factor here. It's a voltage / current, so it's a resistor value, but what do you do when the values aren't from the same source? ie. it's \$V_f\$ and \$I_o\$ ...
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2answers
161 views

Advice for my Voltage controlled Amplifier

In class we are designing a VCA together as part of a bigger circuit. The aim is that we have an input of speech and an input of music and when we speak the the music reduces in volume. The speech ...
2
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0answers
110 views

Unity-gain closed loop Miller OPAMP fails to follow the input after a few microseconds?

I implemented a Miller OPAMP. After I have checked it reaches the desired gain and swing, I put it into the simplest form of closed loop with UNITY negative feedback. The schematic is as follows: ...
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2answers
287 views

I don't understand how the resistor between GND and the source in a common-source amplifier stabilizes it

See this circuit: Applying KVL around the gate-source-GND-gate loop, I get Id = (Vg - Vgs)/Rs. I know the typical argument begins with, if Id increases then Vs increases, but I am not sure of how ...
3
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2answers
147 views

motor feedback system for linear motion

What is the best way to detect the position / displacement of a linear motor ( solenoid type ) for feedback ? I was thinking of using a hall effect sensor or an Infrared sensor .
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2answers
265 views

A phototransistor with LED and resistance in emitter

Earlier I used a simple phototransistor arrangement to detect an on/off signal via a laser pulse. I connected the collector to Vcc(5V), and emitter was grounded through a resistance. The base was ...
2
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1answer
1k views

Voltage regulator with op amp(negative feedback) and MOSFET

The schematic above is a very good voltage regulator, excepting the high power dissipation for Q1 (also I'd use an NPN instead of a PNP). Can I replace Q1 and Q2 with a high current n-mosfet and ...
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1answer
641 views

Feedback for DC Motor Speed Control using PID

I'm working on a project in which I have to control the speed of a DC motor using an analog PID(using op-amps). The input will be provided with a potentiometer. The issue is that I can't figure out ...