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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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1answer
98 views

Prevent current backfeed without power loss

I have a solar panel and an external power source feeding into a DC converter (U10) that are both used to feed a battery charger (U2): In a previous design I used 2 schottki diodes to prevent back ...
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100 views

555 square wave generation with frequency feedback

Knowing that 555's behaviour varies according to temperature, I wondered: In an astable configuration, is there some way to measure output frequency, compare it with some desired value, and use this ...
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71 views

Op - Amp: Linearity, Negative Feedback and Virtual Short

I need some explanations about Linearity, Negative Feedback and Virtual Short for an ideal Operational Amplifier. Precisely, I have been always told that an operational amplifier with negative ...
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102 views

Help identifying component in SMPS

I have been working on a Schroff/Cherokee Europe PE1947/23B SMPS (circa 2004?) and have had trouble identifying a component within the circuit. This SMPS features the following outputs: +12v DC @ 8A ...
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171 views

Amount of feedback in an amplifier

Sometimes I read things like "This amplifier has 30dB of feedback", what figure is that refering to? the \$\beta\$ of the amplifier? or the loop gain \$1+A\beta \$? or the negative feedback factor \$\...
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170 views

What's the largest practical stable gain possible?

I have a feedback application to set the voltage of a node in which there is considerable loss in the loop. Simulations tell me that a differential voltage gain of 10000, 80dB (roughly about what you ...
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261 views

How Replica Feedback bias circuit rejects supply noise?

I attached the circuit diagram along with a short description of its working principle. However, it's not clear how the circuit rejects supply noise. It will be great if someone can brief about what ...
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Interesting Op Amp issue

Good board - bottom view Good board - top view Bad board - bottom view Bad board - top view I am new here and mainly a hobbyist when it comes to electronics. I work more with electricity than ...
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6answers
2k views

Positive feedback and unstability

In Wikipedia's positive feedback article it is stated that given the closed loop gain $$A=\frac{a}{1-af}$$ the system is unstable if \$af>1\$. I don't really get this. If \$a=10\$ and \$f=0.5\$ (...
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1answer
116 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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81 views

Question about the slew rate

Let's consider an op-amp: From basic courses of electronics, we know that the output voltage as a function of the differential input is given by the following picture: Now, assuming that: the op-...
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23 views

Question about a common mode feedback circuit

I'm studying fully differential op-amps. I know from the theory that with fully differential op-amps, unlike the single-ended op-amp, the output common mode is not stable because of unavoidable ...
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1answer
75 views

Question about the common mode

After introducing the two-stages op-amp and frequency compensation for this circuit, during lecture the Professor asked us to find as an exercise a possible polarization of the following circuit: in ...
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3k views

calculate feedback factor in feedback circuit

Below is an exercise with solution about feedback network. I am wondering how the feedback factor is calculated like that. Could anyone shed some light on this?
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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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3answers
71 views

Unity Gain Buffer Initial Conditions

simulate this circuit – Schematic created using CircuitLab A typical way of analysing the unity gain buffer is: Where A is Open Loop Gain Vout = A(Vin - Vp) and Vp = Vout therefore ...
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77 views

SEPIC vs. ZETA feedback

When I was reading through the RECOM book of knowledge DC-DC, I found out that the SEPIC converter has more chance of having resonance feedback than the ZETA converter. They mention that the SEPIC has ...
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27 views

Design Bootstrap Follower

I got confused in the emitter follower circuit with tracking feedback (bootstrap). The mechanism of operation is understandable, but how do I choose the resistor values ​​correctly and optimally? For ...
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0answers
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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1answer
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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2answers
960 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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2answers
71 views

Logic inverter feedback resistor, SPDIF Input/Ouput circuit

What purpose of these resistors? Spdif level about 0.5Vpp. Do I need use feedback resistor if I will convert 3.3V SPDIF to 5V? I want to make 4-way SPDIF Input/Output for WM8805 I2S<>SPDIF ...
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2answers
106 views

How to decouple a negative feedback loop in DC?

My question is open ended, but I provided an example to explain the question better. R19 and R8 in the middle of the pic form a negative feedback loop. They set the gain of the amplifier. I need to ...
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1answer
99 views

Homemade EEG Circuit Common mode feedback

https://sites.google.com/site/chipstein/home-page/eeg-with-an-arduino/assembling-the-arduino-eeg-circult Hi, I am currently building a DIY EEG circuit using the guide above. This guide is for when ...
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214 views

Making block diagram of an op-amp configuration

Hi everyone, I have to make the block diagram of the above configuration. Supposing the input capacitance of op-amp Cin, I've drawn this: A is the open loop transfer function of the OPA. B is the ...
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3answers
104 views

Changing output voltage of a buck converter by electronically swapping the feedback resistors

I am going to design a circuit which is going to output some digital signals. The output stage of the circuit will have some level shifters. The level shifters will give flexibility to the user to ...
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3answers
100 views

I set up an amplifier (LF351) for a gain of 5.7, but it is saturating. Do I have to utilize the offset null pins?

simulate this circuit – Schematic created using CircuitLab The feedback network I am using is a voltage divider with 4.7K and a 1K resistor. The node after the 4.7K resistor is connected to the ...
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46 views

About the differential gain [duplicate]

Let's consider any circuit which contains a differential pair, for example a telescopic cascode single stage OTA: In every circuit like this one, my professor and every book compute the small signal ...
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1answer
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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2answers
95 views

Question about differential signals and feedback

Let's consider, for example, this circuit: During lessons, our professor always assumed perfect differential input (two signals with the same dc value and with equal and opposite amplitudes). As a ...
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1answer
123 views

loop gain, open loop gain of op amp in inverting configuration (feedback capacitor)

I was trying to understand the 2nd answer from this post here, with the circuit of the post shown below. The 2nd answer has equations including open loop gain I wasn't able to understand (1st ...
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1answer
38 views

feedback loop component dc converter

Consider the schematics below, the switching frequency is 250KHz, So, The cross over frequency be 250/5 = 50KHz. My ADC is able to sample at 1MS/s which is good as from the SNR perspective.Now, the ...
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1answer
143 views

Placement of feedback line on DC DC converter, before or after cap? (and dropout problem with LT8390)

I am using an LT8390 DC to DC converter, I have a highly inductive load and it is causing dips. The dips are shown here (and about a 6V drop for 7ms): I need to get rid of the dips, which I will ...
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173 views

Calculating gain of ICF amplifier

I'm designing a circuit with an ICF (indirect current feedback) amplifier, and am trying to calculate the gain of the resultant circuit. Using the AD8237 I followed the example here when designing ...
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3answers
106 views

Op-amp input impedance

I was reading the following tutorial from Analog Devices: https://www.analog.com/media/en/training-seminars/tutorials/MT-040.pdf They include the following image and state: In most op amp ...
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120 views

Stability of Feedback Amplifiers

I'm kind of confused above the stability of feedback amplifiers. Here's what I know In the notes, it says that I don't understand how that's true. I tried deriving it but didn't get anywhere
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210 views

How can I avoid saturation in current source amplifier?

I'm designing a class d amplifier with current feedback as in figure below with the following features: Vbus=50V Iout programmable from 100mA to 1A rms Vout=35Vrms max When the load overcomes the ...
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1answer
45 views

How to select resistance to cancel offset output voltage due to bias current?

Consider the figure above how Rcomp was choosen. I know for simpler circuits like inverting amplifier and ideal integrator how Rcomp was calculated but following same procedure (that's using ...
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1answer
58 views

What is topology of feedback for circuit?

I am confused between Voltage Shunt and Current Shunt Also mention why R2 shouldn't be considered as feedback as it is emitter degeneration resistance Consider the above circuit why can't I consider ...
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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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2answers
99 views

TL494/TL594 measure current with grounded load

Multiple examples of current limiting with TL494/TL594 suggest to use current sensing resistor between load(-) and GND. But I want load to be grounded. Can current sense resistor be placed above load(+...
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47 views

What will be vo/i for given circuit?

Solve using both approaches first using small signal analysis and then using feedback analysis.
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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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1answer
68 views

How to find voltage gain of below analog circuit without using Nodal analysis?

This is a theoretical circuit just made to see that if I can find voltage gain of circuit and it took me much calculations then anticipated to get voltage gain.I just want to find if there is better ...
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What does this circuit do? Op-amp with transistors in feedback

I'm an electrical engineering student and I find this circuit in a guitar amplifier schematic, and basically, I'm just wondering what it does, and how one would go about working out what it does. ...
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1answer
62 views

Powering up second LM386N results in screaming squeal

So I'm definitely a newcomer in the audio electronics realm but I've been really digging into circuits and experimenting with sounds. I've been focusing alot of time working through examples that use ...
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32 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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1answer
41 views

How do I find this value for the feedback fraction?

How exactly do I find this value for the feedback fraction Beta? Thank you. omega_0 here is the natural frequency calculated as omega_0 = 1/RC and s is the complex frequency.
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Difficulties simulating transimpedance amplifier

I am developing a transimpedance amplifier as an assignment for a faculty course and I am running into problems when trying to simulate my circuit in ADS Keysight, even though I am quite sure how my ...
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1answer
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 ...