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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Finding the mid-band gain of an operational amplifier [duplicate]
I am studying for an exam. Been practicing on my professor's past exams and in this one I'm asked to find the transfer function and the mid-band gain. For calculating mid-band gain I'm assuming I must ...
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Using Bode plots for locking a laser to a cavity
I am new to this topic, but I am trying to understand how to use Bode plots to optimize my PID loop parameters for PDH locking a laser to an ultrastable cavity. For simplicity (and based on what I ...
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Op Amp Feedback Resistors
When selecting feedback resistor values in operational amplifiers, how do you optimize the magnitude of the resistors? For example, I calculate the resistor 9/5 ratio value for a gain of 1.8
I know 5 ...
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Given an active filter or any sort of operational amplifier with finite open loop gain, is feedback factor accounted for in the standard gain formula?
To be honest I don't know exactly what I'm calculating here, I know why I'm doing this but I don't know what this expression for gain is exactly.
If I was dealing with an ideal opamp, it's consider a ...
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Understanding GBP, closed loop gain and open loop gain
I'm practicing for my exam so all of this has to be done by hand.
These are the values that I have:
\$ R_1 = 80k \Omega \$
\$ R_2 = 160k \Omega \$
\$ R_3 = 3k \Omega \$
\$ C_1 = 2 \mu F\$
\$ C_2 = 1 ...
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Transfer function of an operational amplifier with finite open loop gain - did I do this correctly?
The open loop gain is \$ A_o= 10^5 \$. I know that generally it's high enough that it can be "ignored" however I'm practicing for my exam and I need to consider it, can't use software either ...
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Having a hard time understanding discrete audio amplifier output stage error corrector circuit, how does it work?
I'm trying to implement a circuit I read about in a book recently, but having a hard time deriving the relationships for the required impedances for error corector balance.
Here is the circuit:
The ...
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If I have an operational amplifier with a finite open loop gain, can I calculate the transfer function neglecting the open loop gain? [duplicate]
I'm talking about this op-amp. In the solution it finds an expression for the transfer function using a virtual short circuit without considering the open loop gain \$ A_{vol} \$ at all. I wanted to ...
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Finding an expression for the transfer function and mid-band gain of a real operational amplifier with a capacitor in its feedback network
I'm studying for an exam and I was practicing on this amplifier, however I'm a bit confused when it comes to a non-ideal operational amplifier.
It's not ideal because it has an open loop gain \$ A_{...
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What happens when the feedback loop is also connected to the non inverting input in an op-amp
I am trying to understand this tone control circuit in a guitar pedal. The image was taken from https://www.electrosmash.com/tube-screamer-analysis:
I do not know how to think about that feedback ...
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Why is the output impedance of an open-loop amplifier with a loading effect calculated by breaking the loop like this?
I'm a bit confused about how the author calculated the output impedance of the open-loop transconductance amplifier with the loading effect as follows.
(All images are taken from of the 6th edition of ...
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Forward-Regulator Feedback
I used this circuit diagram section from TI documents and this is feedback for a PoE controller in forward topology and I read somewhere that resistor R18=50ohm is used to have Bode-plot of circuit. ...
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Applying a voltage by DAC to a Feedback pin of a DC-DC controller
I want to design a variable output voltage in the following design:
For having this variable voltage either I can use a potentiometer instead of R13 or I can apply a voltage by DAC to the feedback pin:...
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What's the deal with this comparator's hysteresis?
I have here a circuit designed by someone else to create a 50% duty cycle square wave that leads a current transformer in phase. The CT maxes out at about 1 amp, and the output of the phase-leading ...
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Can this oscillator possibly work?
I am trying to build a crude RF oscillator. My first attempt, though it simulated fine, disappointingly did not oscillate when soldered together. So, to debug this, I reduced the simulation example ...
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Zener instead of resistor divider on dc-dc converter feedback pin
This dc-dc converter steps up voltage from 3.1V to 7.5V. I'm curious about the unusual D2 zener + R3 resistor to set the output voltage, instead of the traditional resistor based voltage divider. I ...
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I need help to identify the negative feedback loop in a hysteresis comparator
Can anyone help me identify where the negative feedback path is?
I want to determine the feedback factors for both negative and positive feedback, but it's not clear to me where the negative feedback ...
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How to simulate a uniform distribution around zero in LTSpice?
I am using LTSpice for a Monte-Carlo simulation, I typically use the function {mc(x,y)} for componant variability
I also want to introduce spread in the feedback ...
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Op-Amp oscillations when controlling P-MOSFET Vgs
My background is digital design, I guess the answer is obvious for all here, but not for me.
I am studying example of analog physical layer for USB 2 protocol which I found in this paper. Also ...
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Why don't we use an integrator as the loop filter of a PLL?
In a book on phaselock that I was reading, it mentioned that ideally, one would use an ideal integrator as the loop filter of a PLL. Since we can implement integrators with op-amps, why don't we use ...
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Where is the phase shift on this oscillator?
I didn't think the oscillator below could work, but I built it, and it does:
I used 10 uH for the inductor, 2.7 nF for the capacitor, and got oscillations around 8 MHz.
The feedback loop is a series ...
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What requirements of a feedback network are needed to produce oscillation?
I'm trying to understand how to analyze simple oscillators, and would like to know if my conclusions about the required feedback network are correct:
The simplest way to build an oscillator is with:
...
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LTSpice simulation produced different results of phase margin when using step-signal % overshoot technique vs loop analysis technique
I am working on a class AB amplifier circuit to that can output both AC and DC current, controlled by an op-amp with feedback from the final output. The output will be driving an 50uH inductor.
The ...
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How to solve non-ideal opamp circuit using feedback properties?
Is there a neat way to solve this using feedback properties? Or if you know a better method to solve this, please suggest one.
It would be straightforward if we assume an ideal opamp in this case, ...
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MOSFET feedback mechanism
I made an simple feedback circuit. R2 and R3 is voltage divider there so I'm setting them sufficiently big values. But in this setup, it works with 2N7002 and not IRFZ44N (gain is way less then I set ...
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Am I correct in solving this Loading in Voltage-Voltage Feedback
The following circuit is from Chapter 13 of Analog Design Essentials written by Willy Sansen.
Calculate \$R_{out}\$ for this circuit.
Break close loop with loading effect.
$$
(V_{in} - V_X) g_{m1} +...
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Why does this simple op amp create an AM modulated envelope over its carrier?
The circuit below is an ideal op amp (requires no power, can produce any output voltage) in LTSpice:
LTSpice shows it amplifying the 159.155 kHZ input, as expected. But it also shows a 2500 kHz AM ...
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How can you tell whether it's either voltage-current or voltage- voltage feedback?
The following circuits have different feedback.
Resistor \$R_F\$ senses the output voltage and returns a proportional current to node \$V_X\$. Thus, the feedback can be considered as the voltage-...
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TPS65131 inverting dc-dc overshoot
I am trying to make a ±12 V power supply with a TPS65131 DC-DC converter.
The positive rail looks just fine, but the negative rail overshoots to around -12.7 V and then slowly recovers to -12 V, then ...
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How can I break the feedback loop network and add loading effect
Here is the circuit schematic.
Consider Loading effect in feedback and break the loop.
Simplify the circuit.
$$A_{v,open} = \frac{V_{out}}{V_{in}} = -\frac{g_{m1} R_F R_D} {R_S +R_F}$$
Calculate \$...
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How can I analyse this circuit with two port network here?
The following is a figure from 8.72 in Design of Analog CMOS Integrated Circuit, page 319:
The author used Bode analysis in the textbook. I am wondering whether I can solve it with two port network ...
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Feedback of amplifier
Would just like to know, why on the first picture RE1 is "part" of the feedback and is RE3 not? Then on the second picture is RE part of the feedback as well? Is there any way generally how ...
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Feedback of the amplifier
If I have this amplifier with series-series (Voltage mixing , current sampling) feedback- Re, I know that current Ie will be sampling current (output) but what will be the voltage mixing (input) in ...
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NCP11187 - SMPS Design Issues
I have been working on a SMPS design using the NCP11187. It should output 24V DC nominal with a maximum ripple of no more than 100mV Pk-PK and be able to output up to 50 Watts. I have generally ...
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Placing the feedback components close to the inverting input pin or output pin?
In closed-loop operation amplifiers design, should we place the feedback components close to the inverting input pin or output pin in our layout? and why?
For example for this design:
I put the ...
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DSP VS FPGA for Power electronics Solar inverters
I need some help regarding the use of an FPGA or DSP for the control loop of the three-phase solar inverter. I want to implement a digital feedback system (as shown below) instead of analog and ...
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Output Voltage Feedback Circuit interpretation
I see reference design of Texas Instruments PMP40766 Universal input, 500-W CC/CV e-Bike charger reference design , In the design I don't understand the reason of diodes at the feedback circuit I ...
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How can I improve the feedback portion of my boost converter circuit?
I designed this boost converter to drive vacuum florescent displays, nixie tubes, and similar devices.
It can drive a 10k Ohm load at 235V. I'm sure I can get away with larger loads as alot of the ...
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Analog Compensator Vs digital Compensator in Power electronics Converter
I was working on designing a feedback compensator for my buck converter. I decided to use the compensator circuit in the feedback and give its output to Arduino which gives the duty cycle as shown ...
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What does this NMOS/PMOS connected to Vout do in this TIA (Trans-impedance amplifier)?
I was trying to understand a TIA (Trans-impedance Amplifier) design by Behzad Razavi which I found here.
But I don't get what the transistor marked below, which is connected to the Vout, does?
I even ...
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Feedback compensation on a buck-boost led driver
I tried to calculate the compensation network for a TPS92692 in buck-boost topology and I can't find the same value for the typical buck-boost led driver (page 41 of datasheet).
Section 9.2.2.2.12 ...
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About stability in system with loop gain AB>1 in negative feedback
I have been reading about stability and feedback systems, and a very silly issue has appeared.
We can describe a negative feedback system as what can be seen in the following picture:
Image source: ...
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How can I calculate loop gain when considering loading effect in voltage-current feedback?
This is the schematic.
According to the figure from 8.5 in Design of Analog CMOS Integrated Circuit, page 277:
Here we break the loop and add test voltage.
It looks like impossible to find the ...
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How can we identify feedback network in this circuit?
The following is a figure from 8.47 in Design of Analog CMOS Integrated Circuit, page 301:
The book tends to suggests that feedback network
However, I have a different opinion.
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Open the loop in voltage-current feedback
The following is a figure from 8.61 in Design of Analog CMOS Integrated Circuit, page 311:
Here is the question: Calculate feedback \$\beta\$ of the following circuit:
As we use the method of the ...
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How to find feedback coefficient \$\beta\$ of this current-voltage feedback circuit?
Here is the circuit from YouTube:
In order to determine the feedback, we have to break the loop at the gate of M1.
Assume A is \$\infty\$, so \$V_{GS}\$ of M1 is 0. As we know the \$V_S\$ of M1 is ...
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Error amplifier selection
I'm simulating the "voltage error amplifier circuit" referenced from this article
In the article, "Vcontrol" will drop to zero when "Vout" is larger than the reference ...
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SG3525 feedback identification
This is from a UPS which creates 350VDC from 12VDC, How does this arrangement work to control presumably the duty cycle of SG3525?
Compensation (pin 9) and inverting input (pin 1) are connected ...
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Unable to model Transresistance amplifier with feedback correctly
I spent the whole day trying to figure why transresistance amplifier modelled with z-parameters does not match with nodal analysis results but I sill can't figure out. I desperate need help on this...
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How to calculate feedback \$\beta\$ in two common-source stages feedback
The following is from the book Design of Analog CMOS Integrated Circuit, page 307.
KCL at node F.
$$ (V_{in} - V_F) g_{m1} + \frac{V_{out} - V_F} {R_F} = \frac{V_F} {R_S}$$
$$\Rightarrow V_F = \frac{...
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