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Questions tagged [op-amp]

An op-amp (operational amplifier) is a high gain analog voltage amplifier with differential high impedance inputs, and a low impedance output. A basic building block in signal processing, like as amplifier or active filter.

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what is loading error in op amp?

what is loading error in op amp? I have a voltage regulator with zener diode and op amp. why do voltage is low in lower loads for example 100 ohm but for higher loads is not it?
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How does this high impedance circuit stage work

The current i1 flows through Q3 and current i2 flows through Q4. It looks like D5 is trying to mirror the current flowing through it via Q6. D6 is trying to mirror the current flowing through it in Q5....
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698 views

How does an op amp integrator work?

I know there are at least two questions related to this on stackoverflow but neither really answer my question, and in any case, both questions got downvoted. What I am after is an operational ...
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Op Amp Unity gain gives an unexpected constant saturated output

I have this following circuit; I use an Arduino DUE to send a 12-bit DAC output and I want to feed this in an Op Amp. Every ground is tied to the same ground. The Op Amp is ADA4000-2 from Analog ...
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35 views

Why is this voltage follower not working in Proteus?

I have a 4th order bandpass filter which needs to be biased using 1/2 Vcc. I am trying to achieve this using a voltage follower. The bandpass filter was constructed using Multiple feedback topology as ...
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2answers
124 views

Circuit with two opamps

I have the following circuit: simulate this circuit – Schematic created using CircuitLab I need to determine period of oscillations for the given circuit and to sketch waveforms of the ...
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60 views

Can I remove zobel network in LM386 circuit?

What happens if I omit this part? Actually I don't have 10om resistor and I want to know is there any alternative? ps: I know what is a zobel network. I want to know what happens if I omit it.
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102 views

How important is op amp supply cleanliness?

Say I have a simple non-inverting amplifier op amp application as shown. The input signal is far from the rails. Now say the +12 and -12 V supplies are not ideal DC, but rather have lots of ripple or ...
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1answer
42 views

capacitance measurement circuit

For sensing capacitance value of sensors below circuit has common usage in literature. I want to continue talking about simulated circuit in bottom. Could be possible writing an equation similar to ...
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73 views

Can I change op-amp supply voltage without affecting circuit behaviour

I am working on an audio project which is based upon various sections of several different schematics from various old musical instruments. I want to make a test board that has multiple different ...
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38 views

Understanding Optimization/Realization of the voltage controlled current source

I am unable to make a voltage controlled constant current source. So I am using the following scheme (Sorry for bad sketch drawing): The constant control voltage varies in the range of 0 to 5 V is ...
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3answers
86 views

Simple Non-Inverting Op-Amp Problem

I am trying to double the voltage out from a 1.5V battery using an MCP618 op-amp as a learning experience prior to using the op-amp to amplify the output from a set of strain gauges set up in a ...
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23 views

Differential amplifier, superposition theorem, output derivation, what is a loop here?

So based on this article, when V_1 is grounded, in this picture: Is the loop number 1 correct? Or does R_3 and R_4 both belong to the same loop?
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Op Amp Output Voltage

I have a question about an LM741 op amp IC. I am using the op amp as an comparator (open loop with no feedback), as seen below: When the op amp output is low, the output voltage is still around 1.2v....
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56 views

Output problems with lm124 opamp

I am using this circuit to supply current through R1 which is a 50Ohm coil. Opamp is Lm124 supplied as shown in the schematic. Vin is a voltage that can be between 2.5V and 3.5V. Everything works fine ...
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1answer
46 views

How to find the transfer function of this first order active filter?

Going through Design with Operational Amplifiers and Analog Integrated Cricuits, in Chapter 3, problem 3.4 I am asked: The circuit of Fig. P3.4 is a noninverting differentiator. (a) Derive ...
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Efficient and Inexpensive Way of DC/DC 5V to -19V Conversion [closed]

I was wondering if there are any good IC's available for doing this. I have been thinking up some ways to do it, however, I am sure there are most efficient methods. I am not too well versed with all ...
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1answer
54 views

Connecting bandpass filter to comparator generating excess noise

I have a band pass filter with a center frequency of 100kHz, a bandwidth of 10kHz, and a gain close to 1. Input signal is 100mV-150mV peak to peak with frequencies varying from 80kHz to 120kHz. I am ...
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52 views

How does this op-amp photodiode circuit behave?

I am trying to understand the inner workings of a photoelectric object sensor I have in my hands. (modulated with 24 kHz) Here is the very beginning of the receiver part: simulate this circuit –...
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Multisim Transient time point did not converge (peak detector circuit)

I'm building a peak detector circuit with mcp6002 op amp. The signal is 8k Hz 20%dc square wave filtered through a low pass filter whose capacitor varies between about 10pf to 1000pf. The schematic is ...
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3answers
1k views

Why would you need an op amp for reference voltage when the voltage divider does the trick?

Is there a reason this schematic uses an op amp (AD8031) for the reference voltage of the op amp (AD8544) filter when the voltage divider already brings down the voltage anyways? Can the AD8031 op amp ...
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4answers
82 views

Apparent contradiction on ideal OpAmp equations [duplicate]

For an ideal OpAmp the voltages at the inputs are said to be of equal value and the currents 0, however, for we also know that $$V_\text{out}=A(V_p-V_n)$$ but if the voltages are the same the output ...
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Evolving a very simple E-field detector

I'm looking into non-contact solutions for detecting charge (even through certain casings) in passive components. This circuit: is from this site, it works and I've experimenting with a go/no-go ...
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44 views

Non-Inverting Single Supply comparator hysteresis is too wide

I am trying to convert an input sine wave to a square wave. The sine wave is centered at 2.5V and has an amplitude of 200mV, with a frequency of 100kHz. I am looking for a hysteresis of 100mV ...
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74 views

Making LED flash from steady-state signal

I am looking to design a simple circuit that detect objects placed in a spot. So far, the circuit uses simple IR LED and photodiode to detect the object placed between them. The voltage developed in ...
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41 views

Negative voltage supply

I've been trying to make a active load that would use a very small resistor, around 10mOhm as a shunt resistor. I've figured out how to make it, it's a common circuit, however since I need to use ...
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1answer
59 views

Transimpedance amplifier

We have current to voltage converter opamp which has below schematic. Below is the formula to find TP1 Voltage : Vout (TP1) = I1 x R2 or R1 (depend on the switch2 and not calculating the C1) the ...
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1answer
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LTSpice - Voltage Comparator not working

My question is - why is CMP_OUT not going to HIGH (i.e. to 12V, P12V_IN) when INP_U1 is greater in voltage than INP_U2. I think I haven't wired the LT1011 right. Do I have to do anything with the "B" ...
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1answer
58 views

Running +/- 15V opamp at 3.3v

I find I need a comparator, because I have a problem with an optical sensor triggering multiple interrupts, like this question: https://arduino.stackexchange.com/questions/13287/interrupt-fires-...
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1answer
30 views

Measurement of Cmos Parasitic capacitors

i've had a question which asks if we assume that capacitance of capacitors with w/l of 1u/0.5 are then what are capacitance of capacitors (with the actual w/l) now i know cgs in saturation for ...
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1answer
37 views

Common Mode and differential Mode gain of this Cmos diff Amp inverter

This is one of questions our prof gave to students in recent years and im preparing myself for this exam. What is Common Mode and differential Mode gain of this Cmos diff Amp inverter? i understand ...
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3answers
53 views

Is there a circuit that outputs high indefinitely once one high is received by the circuit? [duplicate]

Apologies if the question is worded oddly/weirdly, but specifically I have a comparator with an unstable output which I know could be fixed with hysteresis, but I would rather just have some circuit ...
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2answers
75 views

High voltage gain block

Schematic 1 shows a discrete operational amplifier which is used as a gain block to make up to 450V out of 12V. Q3 and Q4 are used to generate a current which is used by the current mirror. This is ...
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Resistor on transimpedance amplifier input?

I am currently examining an expired patent file of a photoelectric sensor. The file includes the circuit, I am trying to understand it with my limited analog electronics knowledge: Patent no: ...
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32 views

Piezoelectric transducer impedance and phase measurement

I have a circuit comprising of LT1210 current feedback amplifier (supply voltage = +/-15V, gain = 4) and its output is connected to a transformer (RM10 N97) with N=16.6 (150/9) which is further ...
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2answers
52 views

op-amp amplifier for small loop antenna

I’m trying to make myself a ferrite core loopstick antenna for a crystal radio project so I’ve pulled the ferrite rod out of an old radio. The rod is about 1.5 inches and I’ve wound my own coil around ...
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1answer
49 views

Single supply opamp colpitts oscillator

I'm designing a Colpitts oscillator with a single supply rail-to-rail opamp powered with 3.3 V. The positive input of the opamp is set to VDD/2 to offset the negative part of the oscillations so ...
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1answer
50 views

How to find feedback resistor value?

I want to implement typical guitar preamp scheme, like following: I see, that it will have input impendance = 2.2M and ...
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2answers
74 views

Feasibility of custom parabolic mic (amplified, bandpass filtered) for use with mobile phone app [closed]

I am not an electrical engineer, but I am up for a challenge and this is my first venture into electrical engineering. However I am beginning to think this may be a step to far! As a hobby I survey ...
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1answer
64 views

Instrumentation Amplifier - is it possible to have an output signal inverted, with respect to the supply voltage?

I'm doing some circuit design in order to translate a load cell input into the pedal input of a Logitech G27. What I want to achieve involves having a balanced state output as close to 5V from the ...
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3answers
561 views

Op-amp's input bias current

Could you please tell me how do you compute the impedance seen by the inverting input? The result is 100k//1M but according to me the voltage between the 100k and the 1M is not the same. So the ...
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26 views

What is the effect of the signals in output terminal?

I'm using superposition to solve this problem. I already know that for U1 the output is Ua1=-R/R. Unfortunately I'm not sure what is the output for U2 and U3.
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1answer
40 views

DC Gain too low at higher voltages

I am having an issue with DC gain for a non-inverting op amp circuit. All I am trying to do is double the voltage from two DAC outputs (DAC range is 0 to 5V and I want it to be ~0V to 10V). The DAC ...
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2answers
69 views

Stability at loop gain <1 and 180 degree phase shift

I'm reading this article about stability of OpAmps: Link to article. It says: "If Aβ is less than unity at the high frequencies where phase shift reaches 180°, the high-frequency phase-shifted ...
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1answer
23 views

Op Amp Tutorial Pspice missing value

I have this code below for a Amp Op Tutorial from this youtube video: https://www.youtube.com/watch?v=3qE3gL7XbT4. I get the error below for missing value but unsure what is the problem. I'm new to ...
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79 views

Which load resistance is connected to generator U2?

I have this op amp and one of the questions says Which load resistance is connected to generator U2? This is my attempt but I can not confirm if it right. No it's not homework, it examples I'm ...
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This op-amp buffer is oscillating and I can't figure out why

Currently, this is the only assembled part on the circuit board. This is a simple inverting buffer circuit that should be at the input. The op-amp (LTC6241HV) is powered +/-5V from a linear bench ...
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1answer
61 views

Op Amp integrator - limiting +Vsat to zero (ground)

Part of the Dual Slope ADC consists of an integrator which integrates the input voltage according to Vin/-Vref . I am using TL071 connected as an inverting integrator. Quick summary of operation: ...
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76 views

Enhancing the bass response of an audio isolation transformer

Below is a simple buffer circuit using an isolation transformer : The green trace is the output of the transformer and the blue trace is the input signal (20hz to 20Khz sine wave). As you can see the ...
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2answers
45 views

opamp Vos bias resistor

In a simple inverting amplifier I've seen the below topology in my text book, where R3 is said to be R3=R1||R2. However, every time I see this, all three resistors are the same values! From Forest ...