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Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers,

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Resources for learning about transistor configurations?

I'm currently taking a circuits class that discusses various transistor amplifier configurations eventually culminating in building an op-amp. This includes various configurations such as the ...
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1answer
33 views

Pspice simulation of NE5234 op-amp internal circuit. Currently getting zero voltage gain

I'm attempting to simulate the NE5234 op-amp via internal circuits. I'm not currently getting any errors, and so the AC sweep simulation does run, but I am getting 0 V on the output nodes. I'd ...
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28 views

Negative Feedback Operational Amplifiers with Inductors

Wasn't able to find many problems similar to this for reference. I'm studying for my exam next week and am a little lost with some of the material for this section. This is a practice question from an ...
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1answer
60 views

Op- amp input stray capacitance?

I have been wokring on a circuit, where I am amplifying a signal to a high voltage(around 100V) with a frequency of 20kHz but with fast edges. ` The op-amp shown below is used as inverting amplfier ...
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47 views

Delay In circuit

I am working on a mini project using op amp.The circuit uses comparator so when a resistance is changed i.e the Vin is changed(cause I am using Resisters Voltage divider )comparator gives output and ...
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0answers
35 views

Equivalent Circuit of Howland current Pump

Why is at norton circuit for Howland current pump the current source is taken as vi/R1 instead of vi/R0? Because the formula for Norton current is IL=In*(Rn/(Rl+Rn))
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1answer
87 views

Why do not we just decrease the voltage? [on hold]

why do not we just decrease the voltage instead of pulling down a resistor to ground the `68k Ω' I don't know much about this so I'm just learning since the op-Amp LM324 is just checking V1 and V2 ...
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1answer
75 views

How is this equation valid?

I am trying to understand the Howland circuit.But how is the following equation formed .Isnt it should be(vi-vo)/R
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130 views

How to measure biosignals with 1800's technology? [on hold]

Say, you are in a 1800's(all of 1800s) setting where you only have inductors capacitors and resistors and you are trying to detect a signal coming from a persons body. How would you design them? If ...
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75 views

Are my op amp nodal voltages correct?

I am wondering if my assumptions are correct. For the circuit attached I assumed that Va is equal to Vb and which will be equal to Vc since the difference input voltage must be equal to zero.
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2answers
62 views

Differential equation of an OP AMP circuit with RC elements

I have to find the differential equation which describes the relation between input and output voltage for the circuit below. Per how the RC components are arranged, I simply can not find a ...
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2answers
47 views

op-amp outputs supply voltage on GND Signal

I am trying to use an op-amp (first time). I know the basic theory of its amplification circuits. To test I am using an Arduino Nano Microcontroller to create a Signal (0-5V). I want to amplify the ...
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1answer
57 views

Can some one explain me how this equation about op amp came? [on hold]

I dont understand how is the summing of current equation is derived .plz help me to understand it
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31 views

Analog Input Measuring Method [on hold]

I have a question about wiring analog input and measuring method. It seems to me; 2 and 3 wire current analog input wiring is single ended measuring and is going to an amplifier in module that is ...
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1answer
53 views

Voltage divider on differential op-amp

I need to measure the voltage across the R2 (VA - VB) but it is above the common mode voltage range of op-amp. simulate this circuit – Schematic created using CircuitLab How could I do that? ...
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1answer
49 views

Regards Band Pass Filter with AmpOp

I've tried to solve this contest question regards the band pass filter (find the frequency at low-pass and high-pass filters) the picture below: My attempt: I consider that the first stage is 2 low-...
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4answers
68 views

Op Amp: signal measurement that is below its common mode input range

I was wondering, how is possible to use an op amp, which its common mode input voltage is (V-) + 0.2V to (V+) - 0.2V to measure signals as low as 10mV for example? I'm looking for an ...
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1answer
49 views

How can I match phase voltage between a transformer primary and secondary?

I am trying to make a circuit to transform 240VAC, split-phase to a 0 to 5V waveform for an Arduino ADC so I can measure the mains voltage. I have read this question (How to measure line voltage (220V)...
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4answers
61 views

24V DC to +5V and -5V

I need to convert 24V DC to +5V and -5V to power two op-amps (opa2134) and one ATtiny85 with minimal heat generated from the circuit. What voltage regulator would you recommend ? //Digis
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3answers
87 views

How is this circuit a voltage regulator?

I understand how the v_o expression is found, but I don't really understand how or why it's a voltage regulator.
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0answers
71 views

LM324 circuit is not working

My circuit with an LM324 is malfunctioning. I want to build a very simple charge full indicator as well as a low battery indicator (sensor) using an LM324. But it is not working. Below is the ...
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0answers
31 views

Driving an XLR input with virtual ground

I am building an audio circuit. I would like it to have XLR as an input (as well as others). It needs at least 12 Volts to operate. To drive my operational amplifiers, I am using a rail splitter with ...
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1answer
41 views

How to select the best opamp for a constant current MOSFET driver

I'm trying to create a constant current LED driver. I have found and read information about the miller effect and came up with the schematic below. What are the most important parameters for choosing ...
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1answer
55 views

BJT differential amplifier: What causes common mode voltage gain?

In any normal op amp, if it was ideal it would have a gain such that the output voltage would be However in reality this is not the case as there is a common mode voltage gain and hence in reality ...
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58 views

Op Amp-based CV LM317 power supply

As many others before, I'm aiming to build my own simple CC CV lab bench PSU based on the LM317 regulator. Now, I've defined most of the circuitry, but I'm stuck with a particular design choice ...
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2answers
81 views

Converting a variable frequency to TTL HIGH and LOW levels, based on a fixed (possible non-fixed?) frequency

I have a square output from an LM324 op-amp (0 and 5 volts) which has a frequency between 1 to 500 Hz (yes, low frequencies). I would like to find a simple way to have HIGH TTL signal when it is over ...
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1answer
23 views

Variation in output voltage of opamp over time

When i assemble the attached circuit in breadboard and switch on the power supply, the desired output is obtained for the initial 10seconds after which the output doubles. What may be the reasons ?
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2answers
55 views

Op amp with pmos

simulate this circuit – Schematic created using CircuitLab What is the gain (Vout/Vin) for the schematic?
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1answer
84 views

Interesting Op Amp issue

Good board - bottom view Good board - top view Bad board - bottom view Bad board - top view I am new here and mainly a hobbyist when it comes to electronics. I work more with electricity than ...
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2answers
37 views

Calculating resistor values for a Schmitt Trigger and LDR circuit

I am trying to make a light sensing circuit which has hysteresis. I want an op-amp (LM358) to output logic 1 (12v) when the light level rises above 250 lux, and output logic 0 (0v) when the light ...
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1answer
58 views

How to Amplify Thermocouples (and DC sensors between 1mV and 1µV DC)?

This is a bad idea, I know Here's what I know about amplifying really tiny DC voltages: it's impractical to build your own for production there's going to be noise the signal is relative to the cold ...
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1answer
44 views

Unusual Voltage Spike at minimum Voltage Peak

I recently started to get into electronics. I am messing arround with amplifiers right now. I’m trying create a unity gain amplifier. I hooked the amp up to a dc supply then threw in an AC signal and ...
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3answers
546 views

Current sense amplifier + op-amp buffer + ADC: Measuring down to 0 with a single supply

I'm thinking about current sensing with a high dynamic range (10 mA - 20 A) and using LTC6102 as a high-side current sense amp (the voltage would be 54.6 V max, a 13S6P Li-ion battery). ...
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1answer
44 views

Active filter - oscillation and incorrect operation

I have a noisy and low amplitude (0-50mV amplitude) signal from a hall effect sensor (TI DRV5053) that has a ~1V DC offset. The signal will be in the range of 95-105 Hz and is used to determine the ...
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2answers
528 views

How are such low op-amp input currents possible?

I understand that op-amps have low input currents; that's one of their defining characteristics. But looking at the datasheet for the LMC6001 (amusingly called an "Ultra, Ultra-Low Input Current ...
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1answer
48 views

How do some instrumentation amplifiers handle such wide common-mode input voltages?

In a previous question, I asked about the detailed construction of in-amps. Now, I'm curious about a feature that some of them have that I'd like to know how they achieve: I used an INA286 in a ...
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0answers
79 views

PWM to synth control voltage improvements

Just built this little circuit to control my Moog Werkstatt. The plan is to make a MIDI-to-CV converter and add more CV outputs and of course a GATE output later. But before going further, I thought I'...
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1answer
79 views

Why does the 741 op-amp saturate to the top rail when inputs both grounded?

I created the following circuit in MultiSim: It shows a typical 741 op-amp with voltage rails connected to +/-5V and both inputs grounded. With (for all intents and purposes) equal voltages at the ...
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1answer
49 views

overvoltage protection of opamps

simulate this circuit – Schematic created using CircuitLab I see diodes arranged like D1 and D2 sometimes used to prevent nuisance tripping of a power supply's internal overvoltage protection ...
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2answers
124 views

How are instrumentation amplifiers constructed on the semiconductor level?

I'm curious as to exactly how in-amps are designed at a transistor level. They're often shown as being made of three op amps, but due to how specifically the amplifiers are being used I expect that ...
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1answer
114 views

PCB Layout validation [closed]

I'd like to know if the pcb layout is ok for the 2 op amps that i use.I'm interested in grounding and if the op-amps have proper layout(not too long loops or poor ground planes). source files The ...
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22 views

Frequency Modulator with sinusoidal output

I am creating a frequency modulator, all the circuits that I have looked so far on the internet are generating a Pulse wave or a Triangular wave output, so if you guys can help me to create a circuit ...
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3answers
1k views

Strange opamp's output impedance in spice

I'm simulating this circuit in Micro-Cap, which is the clipping stage of a guitar effect. The opamp model is the "NE-5532" I want to measure the input and the output impedance. I expected an output ...
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2answers
67 views

Compensation capacitor(s) in instrumentation amplifier

I wonder whether the discrete 3-opamp instrumentation amplifier requires any compensation capacitors: simulate this circuit – Schematic created using CircuitLab Is it in general recommended to ...
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1answer
61 views

window comparator understanding

I dont understand the output of the window comparator. How does the window comparator switch from HIGH to LOW. There is no transistor or anything else. Only two OPAMP which outputs are put together. ...
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1answer
57 views

Why superposition theorem has not been executed here?

Here is the given circuit In this problem while finding V1 we didn’t took the voltage contribution at that point by Vo(Superposition theorem)Only current source Is has been used to find the voltage ...
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2answers
2k views

Replacing tantalum capacitor with ceramic capacitor for Op Amps

I am trying to build non-inverting amplifier with certain op amp; THS3491 The datasheet is linked below. http://www.ti.com/lit/ds/symlink/ths3491.pdf On page 25, there is non-inverting ...
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1answer
74 views

Electronics project

I am building a project for my college work which is used to detect the leakage of gas in house. The schematic diagram is given below. 1: I removed the rectifier part because I am using a battery. ...
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3answers
137 views

Why the Wien Oscillator output is a sine?

I don't understand why the output signal of the Wien oscillator is a sinusoidal waveform. I can easily understand how a sine waveform can be generated by an oscillator which contains an LC circuit (...
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1answer
57 views

OPA690 Stability

I'm having difficulties keeping this opamp from oscillating and heating up.The schematic is a slightly modified Mini3(mini cube )amp schematic with active ground. A 1nF cap across the 330 ohm ...