Questions tagged [feedback]

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 amplified output.

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431 views

Facing to real world feedback designs (here, Constant Current Generator)

I still work on a current generator made with 2 opamps and a nMOS. If I find the bias point to understand how much my LED can be driven, I still have problems to find an affordable way to derive the ...
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189 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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53 views

Negative Feedback Factor

As of now most of the negative feedback systems I have encountered have a feedback factor that is less than 1 but positive. However in some situations it seems the system can behave as positive ...
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3answers
102 views

How to find input impedance of this OPAMP circuit?

Assume OPAMP to be ideal with infinite gain (a) and infinite input impedance I am clearly able to see that the input impedance of this circuit is R1 (correct me if I am wrong) but I am unable too ...
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107 views

Difference between two integrator circuits

What is the difference between the two integrator circuits? They are used in an amplifier with feedback. There's heaps of information online about the one on the right but not so much about the one on ...
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179 views

Feedback needed on circuit

Could you please give me your feedback on following circuit? . simulate this circuit – Schematic created using CircuitLab Bigger image is available here Explanation in brief: Intention is ...
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2answers
311 views

Feedback capacitor in comparator circuit with an OP-AMP

Greetings, This is a scheme of a comparator with dynamic hysteresis. Green line is the output Red line is the input Blue line is the positive feedback. I want to ask for the explanation why C1 does ...
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111 views

What kind of filter/filters are being used in this feedback loop?

simulate this circuit – Schematic created using CircuitLab I am having trouble understanding the feedback loop for this gain stage for a guitar distortion pedal. I am completely new to ...
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1answer
549 views

Input Bias Compensation for a Comparator

I've been working on designing a discrete dual-slope ADC for school, and I've run into a problem. The schematic below shows my proposed input stage, an ideal integrator connected to a comparator. I've ...
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1answer
171 views

Understanding Working of LC Meter

I am trying to understand working principle of the circuit given in the link below : http://kripton2035.free.fr/Resources/lcmetersch.pdf I realized that the circuit is basically relaxation ...
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4answers
417 views

How can i make a circuit such that output voltage is reduced by golden ratio, using feedback

I want output voltage to equal input voltage divided by phi. Is there a way to use feedback such that i get an exact result? I don't want use numerical convergence with resisters but rather use ...
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126 views

Implementing Feedfoward from a Feedback Control System

In a standard feedback control system, you have a set point, a controller, a plant, and a sensor to enable feedback. The sensor measures the process variable (or in other words, the argument you are ...
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98 views

Does movement along the imaginary axis of a root locus change the natural frequency?

I have two root locus plots (x-real, y-imaginary) of the same oscillating mode: (1) for a base case system and (2) a system with added feedback. They are so similar, almost identical that I am having ...
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265 views

How to adjust output resistance with galvanic isolation?

I need to control the device (lighting LED driver) with 0-10V input. It looks like the driver has 100 uA current source as it can be controled with 0...100% PWM, 0-10V or 0-100kOhm resistance: So I ...
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150 views

Feedback in hybrid power supply

During my research of PSU I came across schematic from Linear's datasheet: 1) Whats the purpose of node which is going from output to SW pin of buck converter? 2) Is node which provides 6V headroom ...
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586 views

Why does a Colpitts oscillator oscillate at a particular frequency?

The feedback network used in the Colpitts oscillator is an LC circuit is shown below. I understand that the phase difference between the terminals 1 and 3 is 180 degrees. Also the amplifier output is ...
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3k views

MATLAB error: “acker” function not returning the same thing as ackermann's formula

I have a discrete time system Suppose I have the following AB matrix of my system $$A = \begin{bmatrix} 0 & 1 \\ 1 & 1.5 \\ \end{bmatrix} $$ $$B = \begin{bmatrix} 0 \\ 1 \\ \end{...
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42 views

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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1answer
132 views

What causes random ringing in my inverter?

I'm currently redesigning the inverter for driving my induction heater. While I've sorted out most problems I encountered I'm still struggling with the actual inverter. Picture 1 shows the waveform ...
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69 views

Active Integrator Parallel Capacitor in Feedback

I am designing an integrator circuit, looking to perform in the range of 10-10kHz - and I had a thought and I cant find any information online about it. For low frequencies of 10Hz, the reactance of ...
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72 views

speed control loop percent error

I'm having trouble understanding the percent error from the following closed loop feedback equations. \$w =1\$ is the road grade change and \$r=65\$ is the speed control input, and given closed loop ...
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991 views

Series-shunt feedback analysis

Microelectronic Circuits by Sedra/Smith present a method to analyze series-shunt feedback circuits by separating the 'A circuit' from the 'B circuit' in which h11 and h22 are consolidated into the 'A ...
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2answers
86 views

Feedback amplifier circuit redrawing

Given the following circuit, I need to redraw it as a Series Shunt feedback amplifier, i.e. with the following topology: Identifying the AC equivalent circuit seems to be easy: 12V and -12V become ...
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339 views

Determining The Polarity of a FeedBack Circuit

In determining the polarity of such a circuit I used the following reasoning: if Vin goes up ID1 goes up and ID2 goes down, ID4 goes down and VG3,VG4 go up because of PMOS, then Vout goes down, if ...
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232 views

Nyquist plot Phase Question

The above graph is pulled from the book "Automatic Control Systems" by Kuo. The subject loop transfer function is $$L(s)=\frac{K}{s(1+T_1s)}$$ or $$L(j\omega)=\frac{-jK(1-jT_1\omega)}{\omega(1+T_1^2\...
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3answers
136 views

Linear regulator loop dynamics

Given a step change in the input voltage of a standard op-amp based linear regulator, a finite amount of time is needed for the op-amp to sense the voltage difference at its input and do whatever it ...
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1answer
137 views

Current controller: how to dampen resonance to increase bandwidth?

I need to design a +/-1.5A, 3kHz small-signal-bandwidth (absolute min, for 3° max phase and 1% max error on amplitude) current controller for a 20 Ohm 0.1H load with a +/-100V supply rail (the current ...
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98 views

Unity feedback gain?

In an example about oscillator In the circuit shown in Figure, \$R_1 = 10 k\$, \$R_2 = 1k\$, \$C = 0.002μF\$, and \$L = 1μH\$. If the circuit is oscillating, find the voltage gain \$A\$ of the ...
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576 views

Noise Isolation tips

I have a device I designed which utilizes 32 SK6812 LEDs (RGBW neopixels). I am experiencing noise in the 1.2khz range (SK6812 LEDs use a 1.2khz PWM signal to control color and brightness) and its ...
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383 views

TIP127 + TL074 power supply doesn't work until I touch it

I have such a schematic based on the TL074 opamp and the TIP127 PNP darlington transistor to control the fan voltage (shown as motor near the D3 diode). VCC = 12V, VDIG = 5V generated by a LM7805. The ...
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71 views

Need help with this feedback circuit (bjt amp)

Could someone help me out with finding the feedback resistor of this circuit. I know for sure RB2 and RL' are feedback resistors but what about RB1/3? Kind regards.
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731 views

Flyback Converter Design Process

I'm kinda new to designing. I have a task at hand which I hope a kind soul is willing to guide me to right direction. I need to design a 2 output flyback converter. First Output would be (12V x 5A = ...
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291 views

Noise/ Oscillation issue in an op amp circuit

simulate this circuit – Schematic created using CircuitLab Currently facing some issues with noise/stability. When a multimeter is connected across Vout and Vref, there is a effectively no ...
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1answer
163 views

Best linear position sensor for piston feedback

I have been looking at measuring the extension/retraction of a piston to record and predict the life of the device. What would be the best way to measure the piston strokes? So far, I have come up ...
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558 views

Current feedback from MOSFET H-Bridge

Hi sorry for the poor schematic. I want to use a MOSFET H-Bridge to drive a linear actuator based on outputs from a microcontroller. The actuator I'm using has inbuilt limit switches so when it ...
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2answers
869 views

Finding Loop Gain (Aβ) of Transimpedance Amplifier

I have been having trouble finding the loop gain (Aβ) of the following transimpedance amplifier: simulate this circuit – Schematic created using CircuitLab To find Aβ, the books I have looked ...
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3answers
285 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 ...
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323 views

Is there a standard symbol for gain margin?

In the context of control loops, specifically power supply control loops in my case, the symbol \$\phi_m\$ is used for phase margin. I've occasionally seen it with a capital M, but on balance it seems ...
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85 views

Developing \$C_{out}\$ spec for DC Bench Power Supply

I'm designing a DC Bench Power Supply, following the general design procedure described by Christophe Basso in his book Designing Control Loops for Linear and Switching Power Supplies: A Tutorial ...
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79 views

How can the flip flop neglect clear when given output is given as feedback?

Here is how the circuet looks. Initally the output the D flip flop is HIGH, when the there is HIGH to LOW input across the multivirator, it create a pulse of 200ms, which is connected to the Clear ...
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3answers
365 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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91 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 gain ...
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405 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 ...
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38 views

Nonlinear Observer Question for BLDC

I'm looking at the article posted here, and I'm trying to figure out what it is that they're controlling and how. Specifically, Dave Wilson from TI gave a presentation called "Teaching Old Motors New ...
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95 views

How to proove if any circuit have negative feedback?

Queries regarding this circuit I am able to say that this circuit has negative feedback but my procedure is disorganized I want a step wise procedure to identify the polarity of feedback In this ...
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100 views

What will be small signal trans resistance gain of shown circuit?

Take beta = 99. I analysed this circuit using first considering this circuit as feedback circuit with shunt-shunt type of feedback and then did the same analysis considering that the circuit is a ...
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31 views

How to Implement this BEMF Observer

I'm using the lecture by Dave Wilson at TI to implement a BEMF observer. I have the motor winding currents for phase A, B and C. I also have the Bus Voltage I also am in the stationary reference ...
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114 views

Output impedance of a series shunt feedback amplifier

I am trying to find the output impedance of a series shunt feedback amplifier by converting it to a two port network. I know the input impedance: Ri=ri*(1+A.β) But I dont know how I should find ...
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55 views

Feedback Circuit schematic to Control Theory block diagram?

I'm studying analog electronics circuit with feedback. I see that, during analysis, a useful abstraction over the schematic is the block diagram in control theory style, but I stuggle in deriving it ...
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55 views

How is this series series feedback topology forOPAMP?

This is stated as series series type of negative feedback but why. Whereas this one is series shunt topology