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 ...

learn more… | top users | synonyms

0
votes
0answers
62 views

Resistive feedback on MOSFETs

simulate this circuit – Schematic created using CircuitLab Two quick questions ==== So, I've modeled several MOSFET-based amplifiers and a lot of them are based on this assumption: if ...
1
vote
2answers
231 views

What conditions could be expected to occur if one or both inputs of an op amp are left floating?

Question 1: Can an op amp work with both of the inputs floating? I assume that due to the input offset voltage if both the inputs are floating, the output would be +Vsat/-Vsat. Am I wrong? Question ...
0
votes
0answers
48 views

Dc-Dc converter

I would like to create a ramp function to compare the output of a dc dc converter with and thus create a PWM signal. Now I have to do this in LTSpiceIV. Any ideas? Thanks in advance
1
vote
0answers
23 views

How to tune PID for a Y(t) = k*X(t) system?

Could I have your opinions on PID type selection? System description Here comes a very simple system: Output(t) = \$ k * (Input(t) + systemVariable(t)) \$. \$k\$ is constant and ...
0
votes
1answer
54 views

Can an amplifier charge itself?

My friend asked me this question and I had no answer. Here is what is proposed : An amplifier is fed a current of, say 1 Ampere. Let's say it amplifies it to 100 Amperes. The output is so designed ...
2
votes
3answers
114 views

Why 60% overshoot with 55° phase margin?

UPDATE: Based on the answers I received, I got this working beautifully. There's a full outcome report in one of the answers below. I'm working through the design of an electronic load, basically a ...
6
votes
1answer
74 views

Should I be concerned when loop gain rises back above 0dB on simulation?

Interim update Okay, I just realized I screwed up on the simulation. When I added \$C_{bp}\$ I upset the "break" in the feedback loop necessary to get the loop gain. The left-side lead has to go to ...
2
votes
3answers
69 views

How do I determine \$R_o\$ for an op amp?

I understand that when driving a capacitive load with an op amp, the output resistance, \$R_o\$, of the op amp interacts with the load capacitor to form a low-pass filter, introducing a pole in the ...
0
votes
1answer
45 views

How do we have a fixed current in this case?

If we are doing a current-to-voltage converter we can use negative feedback on a common-emitter configuration. Using npn transistors would look like so: We are using a fixed current input and it ...
2
votes
2answers
59 views

What can be inferred from the frequency an op-amp is oscillating at?

For whatever reason, I seem to create a lot of oscillators in the course of developing circuits involving op-amps. I'm wondering if the frequency of oscillation, which normally appears to be quite ...
0
votes
1answer
28 views

Feedback Gain Loss of Transimpedance Amplifier

I have designed a single-supply (3.3V) potentiostat that initiates electrochemical reactions, converts the generated electrochemical current into a voltage via a transimpedance amplifier (op-amp used ...
0
votes
0answers
35 views

LTC1923 TEC controller

I'm planning to use the LTC1923 to accurately control the temperature of a TEC. By looking at the LTC1923 datasheet, on page 26 the suggested circuit employs an instrumentation amplifier (LTC2053) ...
0
votes
2answers
40 views

Differential input voltage of op-amp with feedback

I learned that either positive or negative feedback on an op-amp makes voltages at a noninverting input and an inverting input same. Then, I think I don't need to care about absolute maximum value ...
1
vote
2answers
60 views

Current sense in SMPS, how does it work

I've read a couple of application notes where it is stated that measuring current to use that value in the feedback loop helps stability because sensing before the RC net takes a pole away (see ...
0
votes
2answers
82 views

Input impedance of a non-inverting op-amp

From what I've read (and simulated), the feedback loop of an op-amp modifies the input impedance of the non-inverting input. The value specified in the datasheet is the open-loop input impedance, and ...
0
votes
0answers
43 views

Buck Converter power supply based on astable oscillator and zener diode feedback?

simulate this circuit – Schematic created using CircuitLab I've asked several theoretical questions about this before, but I've assigned values and changed my circuit quite a bit. The ...
0
votes
0answers
58 views

Modelling a BJT with easy equations, but having false scenarios

NPN: simulate this circuit – Schematic created using CircuitLab ...
1
vote
1answer
30 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 ...
0
votes
1answer
72 views

transfer function op amp feedback circuit

Does anyone know how to calculate the transfer function for this circuit if Vref is the input an Vo the output? Thank you
0
votes
3answers
64 views

Error in op-amp integrator due to delay in attaining second summing point constraint

An op-amp in negative feedback forces both inverting and non-inverting inputs to the same value. But this takes some time which as per my knowledge is few nanoseconds. So won't this time delay cause ...
0
votes
1answer
30 views

Why should I bother with Frequency Response calculations in a Spilt-rail buck regulator design?

I'm looking at an existing implementation a split rail step-down power supply (application report). I would like to know what's the big deal with frequency response in the reference design? I think ...
0
votes
2answers
65 views

How does a negative feedback amplifier reach steady state?

I tried to simulate a negative feedback non-inverting op-amp, and got incorrect results. I ran the following time-stepping code in python: ...
-4
votes
2answers
117 views

The purpose of voltage-dividers in op-amp feedback?

simulate this circuit – Schematic created using CircuitLab So, here we have a typical op-amp with negative feedback. The non-inverting input is at virtual-ground, and if the input is ...
0
votes
4answers
133 views

Understading negative feedback [duplicate]

There is a question here about something similar, but it's asking about the internals of an op-amp. I'm having trouble understanding the function and use despite several hours of YouTube tutorials. ...
2
votes
2answers
60 views

Why does the feedback resistor change?

I'm looking at a reference design from TI : 18-Bit, 1MSPS Data Acquisition Block (DAQ) Optimized for Lowest Distortion and Noise On page 19, you'll find the following image. It describes the ...
0
votes
1answer
50 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 ...
0
votes
1answer
131 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 ...
0
votes
1answer
182 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 \\ ...
1
vote
0answers
130 views

Would this JFET+op-amp circuit work?

This is Figure 9-3(b) from Motchenbacher - Low-Noise Electronic System Design, so I would expect it to work, but I don't understand it: The addition of a discrete common-source stage at the input ...
0
votes
2answers
190 views

Designing a PI controller for a first order system

I have a first order plant $$ b/(s + a) $$ That I'm trying to control using a PI controller $$ \frac{(K_ps + K_I)}{s} $$ I closed the loop with unity feedback to get this Transfer function ...
0
votes
2answers
36 views

calculate value for resistor in

I have an LMC6001 op-amp, and I would like to build the ph probe amplifier featured in the datasheet. Unfortunately, I am not sure what R9 is or should be. Does R9 control slew rate? How would I ...
0
votes
1answer
64 views

OP AMP as active negative resistors

Was reading about OP AMP and saw a article on "Active Negative Resistor" on wikipedia @ http://en.wikipedia.org/wiki/Negative_resistance. Question to the gurus: How practical is this? Can I build a ...
2
votes
1answer
112 views

Intuitive explanation for this hysteresis circuit?

simulate this circuit – Schematic created using CircuitLab I am trying to get an intuitive understanding of this small circuit. I have both breadboarded it to look at behavior on a scope ...
0
votes
2answers
41 views

Constructing a medical model: logic gates with feedback?

I'm a third-year medical student from Sweden. I am attempting to simulate a specific chain of proteins in a cell using logic gates - specifically, I seek to construct a representation of the ...
0
votes
1answer
37 views

Looking for a LED transmitter/receiver package(or group of components)

I am trying to design a system that utilizes 355nm and 370nm LEDs. I want to keep their intensity stabilized at a certain value, so I want to create a feedback loop. I am using these LEDs as ...
-1
votes
2answers
37 views

Feedback Stability Comparison [closed]

Compare the Feedback conditions given below in terms of stability:- Negative Feedback Positive Feedback with LoopGain < 1 Positive Feedback with LoopGain = 1 Positive Feedback with LoopGain > 1 ...
0
votes
0answers
86 views

Preamplifier active volume and balance control

Hello everyone here is a pre-amplifier with active gain and balance controls, now its a derivation of the above circuit but with added resistors for balance control too. Would do formula for the new ...
2
votes
2answers
168 views

Polarity of feedback for a mosfet circuit

I came across this question in "fundamentals of microelectronics" The objective is to find out the polarity of the feedback. Could someone help me with this? My approach to this question is as ...
-2
votes
1answer
45 views

Feedback Criterion for Oscillations [closed]

In the Feedback equation A/(1+AB) the criterion to be fulfilled is |AB|=1 and phase shift = 180 deg. In this case the poles of 1+AB would be on img axis at \$w_0\$. But in practical cases |AB| is made ...
0
votes
1answer
45 views

Optoisolated Feedback Pin Operation

In the case of galvanically isolated AC to DC converters, a controller IC is used to regulate the output voltage of the converter. The feedback pin is fed a signal from an optoisolator driven by the ...
1
vote
5answers
242 views

Why are feedbacks connected to the negative terminal of op-amps? Example given

I ask this because when I do the nodal analysis for the OP amp in figure 3, I end up with the same results as the inverting amplifier, even though the inverting terminal in figure 3 is grounded. So ...
2
votes
4answers
264 views

How do crystal oscillators work with feedback consisting of CMOS inverters?

For a crystal oscillator to work, there must exist a feedback path with properly designed specifications in order for all to work as expected. Broadly, the basic form of this control system is as ...
0
votes
2answers
297 views

Why there is many configurations of Colpitts oscillator?

I would like to understand how colpitt's oscillator works but I'm confused because there are many configurations on the internet and I don't know what is the difference between them. For the next two ...
0
votes
2answers
131 views

Feedback loops and Logic Gates

Setup: a simple 3 bit incrementer that is both connected to a digital display and to itself simulate this circuit – Schematic created using CircuitLab Assuming that there is no clock to ...
1
vote
1answer
108 views

Generating pseudo-random numbers with restricted hardware

I have a need to generate a 448-bit value that appears random, for use in a test circuit. The "randomness" of the values is not overly important; the size of the generator hardware is. I am using an ...
0
votes
0answers
46 views

Analyze circuit [duplicate]

I asked an INCOMPLETE question and ask again. In the schema below, the input signal comes from a magnetic sensor. The amplitude of the signal is about 0.7 V and the period is 100 Hz. 4066 connect ...
0
votes
2answers
104 views

Can one always drive oscillator inputs with a single-pin oscillator output and bypass the integrated feedback circuitry?

Very little is written in the MCP2211 datasheet regarding the oscillator input configurations. The microcontrollers I have been using lately allow you to use the self-powered, single output ...
-3
votes
1answer
101 views

op amp two feedback [closed]

Hi this circuit have two feedback.input signal is an exponential.amplitude is about .7v and 1/4 4066 switch connect a segment from op amp output.pin 6 connect to a puls and connect a segment from ...
0
votes
3answers
278 views

Why is a gyrator negative feedback?

Consider this circuit, this is a gyrator and acts like an inductor. Why when we analysis this circuit do we use assume negative feedback (i.e. the voltage at each input is the same). I thought that ...
-1
votes
1answer
98 views

Dead-reckoning vs feedback for motor position control of turntable

I am constructing a small turntable that holds a plastic cup and should be controlled to stop at one of eight positions. (Where it will receive a shot of liquid; think "Auto-cocktails"). I'm wondering ...