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Single op-amp with "isolated" positive input pin or method to invert the...
To improve isolation between the input and the other pins of a circuit, I used an MCP6001R SOT-23-5 op-amp which has a pin-out like this:I am interested by the fact that there is quite some space...
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Discrete-Time versus Continuous Time analysis of feedback system
Imagine a generic feedback system, where A is forward gain and F is feedback gain. I will now go over two cases where in i will analyse this system.1. Reference = 110, A=10, F=1In this case, it can be...
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Non-inverting op-amp
Why is resistor R1 connected to the inverting terminal of the op-amp in a non-inverting op-amp configuration? What will happen if we replace it with a short circuit?
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Learning the Art of Electronics 9N.4 -- low-dropout voltage regulator
I have trouble understanding one circuit in section 9N.4 of the book "Learning the art of electronics" by Thomas C. Hayes. I attached a screenshot of that section below.I understand the section is...
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Negative feedback in an opamp
I am a fresher and have been introduced to a basic electronics course at college.Recently our professor was introducing us to opamps and was referring to negative feedback as a rectification to any...
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Individual Phase shift provided by Op-Amp in Closed loop configuration
When comparing the input and output of the Op Amp alone (Vid1-Vid2 and Vo and not Vsupply and Vo) in a closed loop configuration the phase shift is only 90 degrees? Why it is so?And the Simulation...
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Measuring Inverting Op Amp config and not getting desired output (practice)
I am a year 2 EE student and I'm still struggling with getting simulations to work in practice.Components:10k resistor x2ArduinoLM741 Op Amp (pinout:...
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Difference OTA and op-amp
I have a question about OTA (operational transconductance amplifier). Why can an OTA can be used without negative feedback but would still be able to keep its inputs (V+, V-) close each other? I have...
View ArticleLinearity and speed tradeoff with closed-loop feedback
This article describes some tradeoffs involved with methods to increase an amplifier's linearity. One of the ways to increase a circuit's linearity is by applying negative feedback, which converts an...
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Minimizing noise with single-ended opamps
Opamps often get used with one input at a DC voltage, usually the main ground per the standard inverting amplifier example:For low noise, a BJT input stage like OPA1611's is often chosen for the...
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Contradiction between two circuit simulators in measuring open loop gain
I am implementing what I've learned over the past couple of days. This relates mainly to the simulation of a voltage regulator.I built the (roughly) same circuit in both TINA TI and LTspice to...
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Can negative feedback in an opamp circuit be applied to the noninverting...
In figure 1, is the feedback regenerative in nature? If so, can I apply a virtual short to solve it?
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Why are these voltage regulators seemingly using positive feedback?
Looking over LDO / voltage regulator topologies I keep seeing examples of LDOs where the feedback network is connected to the non-inverting input terminal of the error amplifier.Like this:Taken from...
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What is the purpose of including (or excluding) the output resistor in the...
I have often seen (and made) circuits like this. It is a simple inverting op-amp buffer, plus a small current-limiting output resistor to protect the the op-amp if the output is shorted.simulate this...
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Emitter follower
I'm having a hard time understanding an emitter follower. What I don't understand is why there is no voltage gain but only current gain. From my understanding when the transistor is turned on, the CE...
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I don't understand this temperature controller circuit's behaviour [duplicate]
I am trying to build a circuit to regulate temperature for a few microheaters. Here's the circuit I am using:This is a constant temperature controller circuit often found in the research papers and...
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How to determine if the feedback is positive or negative?
How to know if I have to apply the formula Af=A/(1-AB) [positive feedback] or Af=A/(1+AB) [negative feedback]?
View ArticleWhy, in a negative feedback amplifier, do the op-amp input terminals become...
The equation from the model of the functionality of the op-amp is that$$V_{out}=A_{0}(V^{+}-V^{-})$$In case of negative feedback, \$V^{+}=V^{-}\$.Why do the two terminals in case of negative feedback...
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Is there any guide how to design and bias transistor amplifiers with negative...
I was reading the ARRL Handbook and came across RF transistor amplifiers with negative feedback, which seemed interesting. However, there was no information provided on how to properly bias these...
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Constant current source with transistor
I have this circuit that should describe a constant current source. From my point of view the pnp-transistor has to work in its saturation mode. Thus the potential on the emitter should be constant....
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How to break the feedback loop and add the loading?
I am trying to break the feedback loop of a fully differential amplifier and add the loading to the input and output:I want to do this to take into account the loading of the feedback network on the...
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Gain of a negative feedback circuit (problem)
I am asked to find the gain A for this negative feedback circuit below:(A: gain, G: all of the gain of the circuit, F: return ratio)The simplified circuit above shows the gain A that I am trying to...
View ArticleThe influence of negative feedback on input resistance and bandwidth
I'm interested in how negative feedback affects bandwidth and the cutoff frequency.Is the cutoff frequency always increased by (1-Ab) times?fg_r = fgo*(1-Ab)?Does the same apply to input resistance?
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How to analyse this with nullor block?
The first is the schematics from NMOS4 with parasitic capacitance:I recently read an article on how to analyse the circuit with The Nullor and Some Applications.The equivalent nullor circuit. I am not...
View ArticleHow does the op-amp stabilize?
I have a problem understanding one thing in op-amps, namely - when the cycle of stabilizing ends?For example, when we have simple non-inverting amplifier, firstly the difference equals the amount of...
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What are the necessary conditions to prevent latch-up problem for Oscillators?
In his chapter on oscillator design, Razavi discusses the issue of latch-up and proposes several methods to eliminate it. However, he doesn't provide explanations for these methods. Could anyone...
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Understanding Op-amp Negative Feedback
Have a look at the diagram above. It shows an op-amp with negative feedback. Ignoring the feedback loop for now, the voltage (pressure) coming from the 5V battery, acting on the inverting pin, should...
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How to prevent this op amp from railing
I am a beginner.I have the following circuit :An input that can go negative (+/-5V sine wave), and two inverting op amps. The second op amp is "current buffered" it is driving the base of a BJT.Here is...
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Using an op-amp to drive LEDs according to an incoming signal
The following schematic was suggested for visualizing the frequency (which is variable) of an oscillator using two LEDs that light up alternatingly. It seems that the value of the resistor determines...
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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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