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 ...

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63 views

How does this sample and hold circuit work?

What role does the 30k resistor play in the LF398? How would that resistor eliminate any offsets introduced by the op-amps in a circuit like this one: On this ...
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1answer
51 views

FPGA design rules - Using a Module Output Register Value Internaly

I'm trying to optimize a verilog code and I found something that I don't feel it's correct. I found a module that has an output and it's using that output value as a condition in a case statement. ...
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1answer
28 views

Feedback Control: Unexpected result for block diagram simplifications using matlab

I made some simple calculations regarding block diagram algebra. The problem is that I don't get the same result using matlab. Here is the system with it's corresponding blocks: $$H_1 = z+2$$ $$H_2 ...
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4answers
108 views

Negative feedback using op amps?

I never quite understood why negative feedback is more used than positive feedback. Using feedback makes it possible to adjust the gain, and thereby specify how much the input should be amplified. ...
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2answers
104 views

Why is this amplifier inverting that voltage?

Can somebody please explain to me why the output here is the negative of the "input"? I really can't wrap my head around it...
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83 views

Current Series Feedback Calculation Puzzle

I'm following a text on negative feedback amplifier analysis and the author describes the following example of a current (sampling) series (mixing) feedback circuit; the humble CE amplifier: ...
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1answer
69 views

Pull-up resistor causing unintentional voltage divider?

I'm trying to use the output of a comparator as the input of a schmitt trigger built with positive feedback on another comparator. Both have open collector outputs. When the two are not connected, ...
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1answer
53 views

Making a Radio Work

I am new at electronics and I decided to try my hand at making a radio. There seems to be a dearth of material online to actually explain practical radio construction. I built a radio given in the ...
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1answer
98 views

Why Bandwidth Affects Response Speed

This is a follow-up question to (this question). Here is the amplifier section in question: In the answer, the author (@Brian Onn) gives the following explanation: "Slow vs. fast is not about ...
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0answers
46 views

Can the input voltage be larger than voltage power suply in OP?

I have this scheme, and I think that it's incorrect, because I think that this current path can't go on 7(V+), than we need same but oposite sign on 4, and it should go on output of the OP. Am I right ...
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2answers
78 views

Transistor Based Amplifier and DC Only Negative Feedback

My analysis of Heathkit RLC Bridge continues (previous question here). This time I've been trying to analyze the feedback amplifier section shown below and taken from the original document IB-5281 ...
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2answers
41 views

How do I calculate phase margin for a feedback amplifier

I'm learning analog design and can't seem to get a firm grasp on the concept of phase margin and wanted to ask a few questons: First Part: I understand that Phase margin is the difference between ...
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2answers
66 views

Phase Locked Loop: Confusion in Lock Range

For Phase locked loop (PLL), we can have two types of Phase Detectors (PD): Type-1 and Type-2. The Type-1 PD has an analogue multiplier (which is simply XOR for digital inputs) whose low pass ...
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1answer
42 views

Confusion: Lock range of PLL

Suppose we have a type-I PLL whose block diagram is shown below: Here \$k_{pd}\$ is the average gain of the phase detector producing the control voltage \$V_c\$ which is input to the Voltage ...
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4answers
52 views

Barkhausen condition on a Wien oscillator

Consider the Wien oscillator: We can determinate the operational amplifier gain defined as: $$A(s)=\frac{\bar{V_o}}{\bar{V_a}}$$ and the gain from the feedback network: ...
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1answer
63 views

Determination of System poles through open/short circuit time constant technique

I was reading about the open and short circuit time constant technique for estimating the dominant and non-dominant poles of the system respectively. For the dominant pole (open circuit time constant) ...
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3answers
83 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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3answers
143 views

Selecting a capacitor for use in feedback loop

I'm designing a DC Lab Power Supply; the voltage regulation circuit looks like this: I'm developing the BOM, component by component, and next in line is specifying the capacitor in the feedback ...
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2answers
227 views

Adjustable 0-5A voltage controlled current source

I would like to build a high side current source that can source 0-5A with a 1mA resolution. The voltage source feeding into this current source is a variable 0-50V that is always ~3V above the ...
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2answers
102 views

Delay and Stablity in Negative Feedback Systems: Confusion

Below is a block diagram that shows an op-amp in negative feedback with feedback network made from resistive divider: The encircled block is Op-Amp with 1 and 2 as its inverting and non-inverting ...
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2answers
48 views

Feedback resistance condition (Rf > 29R) in Phase-shift oscillators

In an equal resistance , equal capacitance CR phase-shift oscillator, the feedback resistor has to be slightly larger than 29*R When I am attempting to simulate the circuit at 29*R, there's ...
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0answers
44 views

Modeling a feedback loop in spice

I'm having some difficulty with an asymmetric half bridge design. I've never been great with control loop theory, and I'm wondering what the best way to figure out the R and C values for the feedback ...
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1answer
43 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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2answers
98 views

Systems stability with zero poles

I have a rather simple question I would say. I know that systems having real poles to the right side of the plane will inevitably be instable (for LTI systems at least). But I'm confused with ...
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0answers
26 views

direct feedback from drain to source oscillator

I am reading about one transistor LC tank oscillator. Here is a picture of that circuit: The tutorial file says "direct feedback from drain to source". I don't see why. It seems to me that there is ...
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3answers
91 views

Can you switch between 2 tank circuits using a relay?

Say I have an oscillator that needs to span between 1 GHz and 1 Mhz. Ill be controlling it with a microcontroller, probably an arduino. According to this, ...
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3answers
446 views

Bandwidth of inverting and non-inverting op-amps

If the same op-amp is used in both inverting and non-inverting modes (with same closed loop gain using appropriate resistors), will the closed loop bandwidth of the op-amp in both cases be the same? ...
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2answers
107 views

How do I take the larger of two analog signals?

I have two feedback signals. I want to create a circuit that outputs the larger of the two. I know I could do this with diodes, but I'm unwilling to accept the diode drops. I suspect some op amp ...
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41 views

midband gain calculation of feedback amp

I cannot wrap my head around this. how did they calculate the gain of Q1? can anyone explain the big picture? the math is already shown but I cannot see the breakdown of it. rpi1=2.3K and rpi2=1.23k ...
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3answers
64 views

Help understanding negative feedback & bias design on audio amplifier

Please take a minute to look at the audio amplifier diagram below: In case it helps, the diagram comes from a do it yourself Velleman 7W Mono Aplifier (K4001) kit. The amplifier is based around the ...
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2answers
52 views

Gain of Basic Amp with FB network

the goal is to find the gain of the circuit. I don't understand the Vi/Vs part. I know they used voltage divider, but why they included the second term(in Red) in the expression? where does that come ...
2
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1answer
75 views

Is it possible to make a non-inverting amplifier with positive feedback?

The 'classic' non-inverting amplifier configuration uses negative feedback. What happens when the + and - terminals are switched? Based on my pencil-and-paper analysis and a Circuitlab simulation, it ...
6
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1answer
138 views

Have current feedback op amps gone out of fashion?

Or have they perhaps always been a bit of a niche product? I've been working with op amp circuits on nights and weekends for about a year now. It was a fair amount of time before I encountered a ...
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3answers
67 views

What is meant by 'modified forward path' in this op-amp problem?

What is a modified forward path? In the practise exam paper I'm doing I'm given this circuit and asked to draw an equivalent circuit of the 'modified forward path amplifier'. I'm told that it ...
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2answers
112 views

Why sample current via lopsided resistive divider?

I'm studying the constant-current circuit of the Agilent E3610A 15V 30W DC Bench Power Supply. The entire schematic is at the end of the user manual, but I've redrawn the parts of interest here for ...
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0answers
97 views

Deriving PI controller transfer function when input is reversed

I'm developing the compensator for the linear DC Bench Power Supply I'm designing. As I've come to deriving the transfer function for the op amp-based compensator, I realize I've been depending on a ...
4
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2answers
443 views

Input voltage for feedback pin on LM2596 Voltage regulator

I am using LM2596 for a dc supply where I could alter the output voltage. Datasheet here. I have setup according to page 9 "Adjustable Output Voltage Versions". Everything worked fine. The output ...
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1answer
97 views

What is an “origin pole”?

I'm studying Christophe Basso's book Designing Control Loops for Linear and Switching Power Supplies. In the book, he often uses the term "origin pole". This is what I think I understand about it so ...
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2answers
130 views

Is a Type 2a PID(ish) controller just an example of an augmenting integrator?

In a previous question I finally cracked the code on deriving for myself the transfer function for a Type 2(a) compensator like this one, built around an op amp. As it turns out, for AC analysis ...
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2answers
183 views

What is this RC local feedback configuration?

I'm studying power converter control loops using Christophe Basso's book Designing Control Loops for Linear and Switching Power Supplies. A very common pattern in the compensator circuits is a ...
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1answer
69 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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1answer
63 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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0answers
63 views

Feedback to control boost converter circuit

I'm trying to implement the last part of a research paper about electrovibration. At present, I have a flyback transformer generating ~100V AC, which is being modulated by an MPSA42 BJT NPN ...
6
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3answers
323 views

Pass device selection for bench DC power supply

I'm designing a DC Bench Power Supply. This one will be 0-30V, 0-300mA, but I expect I'll try some heftier models once I've gotten this one worked out. I'm following the general design procedure ...
7
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6answers
681 views

Step-by-step explanation of how voltage follower reaches steady state using negative feedback

Just one minute! I am not trying to understand what negative feedback does eventually, or why it should be used. I am trying to understand how the circuit reaches steady state, and how, step by step, ...
2
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1answer
68 views

Low voltage cutoff circuit with USB reset

I am currently trying to design a circuit for a low voltage cutoff. Once the voltage dropped below a certain threshold it should stay low. When a USB-cable is attached it should reset and start ...
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1answer
53 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 ...
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2answers
136 views

What is meant by the break frequency of an op-amp?

1.Can someone explain me the break frequency of an op-amp and can an op amp have two or more break frequencies, if so how?
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2answers
252 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 ...
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34 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 ...