# Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers, which are DC-coupled, high-gain electronic voltage amplifiers with a differential input and, usually, a single-ended output.

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### Implementing Inverter op-amp, calculating impedances in multisim

Consider the following circuit , i have couple of confusions before asking the question, so suppose the source Vin has a frequency of 1kHz and amplitude of 50mV, and also we set the potentiometer to 0%...
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### Input/Output Impedance for ALI

Consider these circuits from Paul Horowitz "Traité de l'electronique" page.238: I want to derive the expressions they made for $Z_e, Z_s$ for both circuits: So I think the op amp is ...
151 views

### What is wrong with my OpAmp Circuit Calculation?

The Question: My Workings: My Mathematica Output: I am attempting to solve this problem using KCL, can someone tell me what I am doing wrong? My mathematica code is not outputting anything. Thank ...
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485 views

### Practical Multiplier circuits using log/anti-log amplifier

I'm trying to build a circuit that output the product of the 2 inputs using TL974 opamps. Looking for something like Vout = Vin1 x Vin2. I found this design which should give something like Vout = ...
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### Improving the waveshape and amplitude of a saw-tooth generator

I am a student in in college level physics and so I do not have a lot of knowledge when it comes to circuits and the different electrical components. Still, as a project, I decided to try to build an ...
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### Op amp as a comparator output turning partially high when it's supposed to be low

I'm using an AD823 op amp, as a comparator as part of a feedback loop in a boost converter. Although the boost converter and feedback portion functions as desired, the problem is when I check the 13 V ...
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1 vote
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### Input ranges exceeding rails in opamps & comparators

With opamps & comparators datasheets I've seen, it was typical to show in absolute maximum ratings values such as: $$V_{SUPPLY} (V_{DD} \; to \; V_{SS}): \quad 12V$$ V_{DIF\_IN} (V_{-IN} \; to \;...
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### Proving the output voltage expression [closed]

Assume this is an ideal op-amp, we consider the bias currents in this circuit; consider also Ve = 0 : I want to prove what they wrote in the solution : So what i will do is using the basic tools i ...
101 views

### Removing GND and Power planes under the feedback pins and traces in opamp layout

I want to use a reference design form Texas instrument as a reference for my layout for OPA838, I noticed this reference design is a 4-layer board (signal-GND-Power-signal): Reference: the image is a ...
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### High-speed counter for Arduino

I need to count electronic pulses that last around 3 ns with an amplitude of 1 V. They arrive at random times, with usually a separation of more than 100 ns. The counted signal should not have a high ...
1k views

### Diode clipping question on output of opamp

I have been trying to implement a basic hard-clipping circuit for a distortion guitar pedal, based on two simple diodes, but somehow I can't get it to work as it is supposed to be. The basic design is ...
1 vote
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Hello, I am trying to find out output resistance of opamp. Is the way that put the small signal model source at the output, set the voltage at operating point 0.9028V, and set the AC amplitude for 5mV....
804 views

### Filter non-inverting input of operation amplifiers or directly to GND?

In the following configuration on this operation amplifier (OPA838), which is transimpedance configuration, can I connected the non-inverting input directly to GND, or should I use this filter? Not ...
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### small signal overshoot reported in datasheet and stability

In datasheets of some op-amps namely ADA4522, NE5532, OP184 a small signal overshoot percentage has been reported mostly for an input pulse of 100mVp-p in a unity gain configuration. As far as I ...
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1 vote
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### Choosing isolation resistor for Op-amp output

I want to choose an accurate value for an isolation resistor for my OP-AMP (OPA838). Based on the datasheet, the OPA838 is very sensitive to capacitive loads and needs an isolation resistor added to ...
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### Configure an op amp with 500 v/v gain with at least a 1k load

I have been working on an optional differential op amp using BJTs and cant seem to achieve the above goal. I have a current mirror in place and have been trying to configure the circuit below to ...
111 views

### How to use the AD829 Op-Amp? (Weird "auto" output)

I have an AD829 Op-Amp, which I have tested in LTSpice with this circuit/output: In this simulation I'm amplifying a 6mV signal at 110MHz with the AD829. I have tried this circuit on a breadboard ...
101 views

### Class AB amplifier with opamp

https://www.nutsvolts.com/magazine/article/probing_cores While studying this circuit for driving inductive load, the author has wrote opamp cannot provide bipolar current,does he mean source and sink ...
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### What is the difference between using op amp and transistor for small signal amp? [closed]

I have a question. As you know, not only the transistor can be used for switching level or amplifying small signal (single or multiple stage design), but also op-amp can be used in same purpose. So ...
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263 views

### Anti-aliasing filter for 3.3 V ADC at 1 MHz

I am designing an anti-aliasing LPF for a 16-channel ADC on a custom STM32F415-based board. This design will ultimately be put on a car and used as a DAQ. I am planning on running the ADC with a 30 ...
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1 vote
276 views

### Band pass filter zero crossing distortion

Second stage output Drawing I built the above bandpass filter using lag lead combination for filtering +/-2.5 Vp-p square wave @ 125 kHz, but the extracted sine wave have zero crossing distortion,...
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### What is the right capacitor amount in this circuit schematic?

I got this schematic in the manual of the gas sensor provider. The sensor is Winsen ME2-C2H5OH-Ф16. The schematic is the application circuit for reading the fuel cell sensor, using an op-amplifier. ...
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### Two stage differential amplifier as comparator [closed]

I used two stage differential opamp as comparator but I'm getting the output -ve voltage range. I have to get high (1.8 V) when it is greater than reference voltage and low (0 V) when less than ...
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178 views

### Confusion about finding poles by inspection

I have a few doubts regarding finding poles by inspection and why sometimes the 'quick, intuitive' techniques do not work. Question 1 Consider the circuit shown in figure 1 below: By manually writing ...
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### Output of op-amp in Multisim and CircuitLab

I have two identical circuits of op-amp one in MultiSim and one in CircuitLab. They show different current out of the op-amp and I am not sure why. Here is the MultiSim circuit. In case it is not ...
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### What Vin should I use to create a PI controller to stabilize an error of a signal?

In this design I am making an incubator, in such a way that a temperature sensor sends a voltage to two comparators that decide whether a fan or a light bulb should be turned on to always maintain the ...
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### Inverting Op amp do i need a pull down resistor

So im currently working on a circuit and im not too familiar with inverting Op amps and therefore am asking for some help below is my circuit its the latter half of the circuit and just wondering if i ...
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### How to make an active crossover Opamp filter an audio signal

Background I've built a few passive crossovers, but never done anything active and my electrical skills are newb at best. I wanted to test out an active crossover after reading into by-amping a stereo ...
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### Seeking assistance with the circuit design for Force balance geophone

I am attempting to DIY this patent article, configuring the circuit based on the method provided (Fig. 1). I've configured the circuit (Figs. 2 and 3 and VIDEO). In my experiment, once I connect the ...
1 vote
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### Implementation of Op-Amp

I want to implement this circuit in multisim, i fail to do so, because first im not aware of the internals of this circuit, i dont understand whats the purpose of R14 and whats the purpose of VR1 and ...
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I designed an amplifier with an OPA838 as follows: First scenario: I want to connect the OPA838 to a next stage voltage LNA (Low Noise Amplifier). What components or circuit should I add to my output ...
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### Should I use an op-amp buffer so I'm not affecting the original source's current requirements?

I'm attempting to modify an existing product (a dance stage similar to Dance Dance Revolution) where the panel signal is held high (5V) and when it is pressed it pulls the signal low (0V.) Only High (...
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### Transimpedance amplifier oscillating at high gain setting on PCB only

I am trying to make a bare minimum transimpedance amplifier for a very large Si photodiode (Thorlabs FDS1010). My circuit is just like in the picture except my digipot is an AD5272-100kohm and my ...
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### How can I convert a sine wave generated by PWM technique into a square wave?

I have generated a variable frequency sine wave by PWM using an Arduino Uno. I want the obtain a square wave using the generated sine wave, so I used an op-amp to remove the DC offset in the sine wave ...
114 views

### Amplification for digital caliper

I am making a DIY digital caliper, more on the project you can find here. From various places I found how to design the patterned for the PCBs and with a scope I measured existing calipers to ...
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I am designing a circuit with 3-stage cascading op-amps, followed by a band-pass filter, for a signal centered at 1 MHz, as shown below. My signal generator can't generate a signal below 2 mVpp, ...
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### Avoid cross talk between recording electrodes

I am trying to compare two record signals coming from two INA amplifiers simultaneously. Both amplifiers are actually recording the same signal, just with different recording electrodes. We are ...
1 vote
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### Multiple-stage op-amp signal distortion

To test it - I changed the gain to be 5 instead of 100, but it still didn't seem to work as expected. Is there anything wrong with the way I am coupling the two stages? I am designing a two-stage op-...
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1 vote
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### PCB layout recommendation for Op-Amp [duplicate]

When designing a PCB for Op-amps normally there are some guidelines in the datasheet of the device. For example, for OPA838 the suggestions are: Signal routing must be direct and as short as possible ...
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### Investigating the effect of PCB layout parasitic in an op-amp amplifier by simulation

Would you please let me know what components I should add to my schematic as result of PCB parasitic to make my simulation more accurate? As an example, the following image shows an amplifier ...
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1k views

### Why is a peak in the gain a sign of instability in a closed loop op-amp circuit?

I watched a tutorial video that mentioned that when there is a peak in gain (dB), it is a sign of instability in the op-amp circuit. Is this statement always correct? If yes, can any one please ...
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1 vote
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### Modulation Bandwidth of LED

Following on my previous post I have photodiode connected to OpAmp in inverting transimpedance configuration. (Circuit diagram can be found in previous post). Excitation source is 4000K LED with ...
917 views

### Op-amp (LM348N) becomes very hot when connected to power

Is it normal for an op-amp to become very hot immediately when I connect its power pins? Nothing else is connected yet, just +5 V to the VCC+ and GND to VCC- pins. I never used an op-amp before, just ...
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### Analysis of the below op-amp circuit and its waveform

What will be the output voltage and capacitor voltage waveform for this problem? [The approach I tried --> When the diode is ON, the negative feedback is complete and voltage of inverting terminal ...
1 vote
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### How to calculate values for current and voltage limiting resistors in variable power supply?

I have an assignment, where I have to calculate the values for a current limiting resistor (R3) and a voltage limiting resistor (R14) for a variable power supply. The input voltage to the circuit is ...
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### Adding a capacitor to the output of an op-amp can cause instability? (PCB trace capacitance)

In my amplifier design, I checked all the possible issue for finding the instability problem in my previous post: Transimpedance amplifier with OPA838 - oscillation - supply voltage , Transimpedance ...
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### Current-to-voltage converter not reaching expected Output

I have this circuit: (Current-to-voltage converter, second circuit on this page) The OpAmp is lm358A (datasheet) The Supply voltage of the OpAmp is +18V and -12V For Rf is used 500 Ohm Iin = 20mA Vout ...
1 vote
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### OpAmp Offset Null Pins in LTSpice

I'm simulating the following circuit, where the Op Amp is an LM741: The LM741 is an 8-pin device, and this design calls for using 7 of them. From the datasheet, here are the pin connections: I have ...
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### Driving speaker with differential driver

I am designing an battery powered device (3.6-4.1 V regulated down to 3 V) which plays audio recordings through a speaker (8 Ω, 0.3 W). I want to drive the speaker by applying two differential inputs, ...
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