# 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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18 views

### Design Bootstrap Follower

Help, got confused in the emitter follower circuit with tracking feedback (bootstrap). The mechanism of operation is understandable, but how to choose the resistor values ​​correctly and optimally? ...
33 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 ...
93 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 ...
918 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 ...
50 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 ...
104 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 ...
95 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 ...
179 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 ...
102 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 ...
90 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 ...
45 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 ...
52 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 ...
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 ...
117 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 ...
35 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 ...
120 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 ...
162 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 ...
60 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 ...
95 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 ...
119 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
201 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 ...
44 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 ...
56 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 ...
95 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 ...
68 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(+...
44 views

### What will be vo/i for given circuit?

Solve using both approaches first using small signal analysis and then using feedback analysis.
96 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 ...
67 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 ...
4k views

### 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. ...
60 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 ...
25 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 ...
35 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.
47 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 ...
43 views

### 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 ...
230 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 ...
70 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 ...
52 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 ...
121 views

### 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 ...
90 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 ...
79 views

### Finding the negative feedback loop in the amplifier circuit

Today I was learning about the negative feedback in the amplifier circuits and some quick ways of discovering whether a negative or a positive feedback exist in the circuit by finding a feedback loop ...
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?
19 views

### CMFB - wide devices reduces voltage drop?

In the above CMFB using triode devices, one of the drawbacks is stated as being a limited output swing due to the drop of the triode devices (acting as resistors) M7 and M8. It says in the ...
24k 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 ...
125 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 \\$\...
968 views

### Which CMOS logic families can safely be used to construct linear circuits?

I've just learned that digital CMOS inverters can be configured to perform analog functions (most notably oscillators and amplifiers). However, many of the examples tend to favor old CD4000-series ...
42 views

### How does not using common-mode feedback drive my outputs to the rails?

Consider the following circuit in Fig 9.31 (a) Now, essentially, summarising the block of text, it seems that due to some mismatch between PMOS and NMOS devices or fluctuations in bias voltages, the ...
54 views

### Explanation on why there is no feedback in the circuit for higher voltages of input signal

simulate this circuit – Schematic created using CircuitLab I don't understand the reasoning behind the analysis of this circuit. The professor started by saying that if diodes D2 and D5 are ON ...
119 views

### Proportional Control Balance Beam

Bit of an unorthodox question I'm sure, but I'm making a balance beam (two rotors on either end of a see saw) with proportional control, and I can't seem to get it to balance at 0. The proportional ...