# 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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### Realize transfer function with Op-Amps

I have this transfer function: $$H(s) = 15 \cdot \frac{(1k)^2}{s^2+500 s+(1k)^2} \cdot \frac{s+40}{s+300}$$ I separated it into two stages, diving the $k=15$ so that both transfer functions have ...
1 vote
36 views

### How can I design a heart-pulse-sensing circuit using a BPW34 photodiode?

I tried to build this circuit that I found online: After I built it, I don't think it was working properly. I tried measuring the op amp output with a multimeter, it was very small (below 0.300v) and ...
572 views

### How does an op amp amplify things in respect to its electron flow?

I'm a newbie learning about electronics for fun. While I was doing some, research I bumped into operational amplifiers. Unfortunately, no matter how extensively I looked at different resources I could ...
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### High current voltage controlled current source MOSFET selection

I am working on adjustable voltage controlled current source (2 to 3 A) for my project. I tried different NMOS for the projects, but they all burned. In my application, the resistance of my load is ...
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59 views

### Impedance of a real op amp

I am reading the book Operational Amplifiers by Steve Winder. On page 14, it explains input impedance of real op amps: "... there is a large differential input impedance ... ". How exactly ...
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### Operational amplifier

Hello everyone! I have this exercise to solve and I don't know how! This is an ideal operational amplifier and from the theory I think V+ = V- and i+ = i- = 0 The first thing I did and I think it is ...
142 views

### Does the MOSFET go into the linear region when the op-amp goes into saturation?

Consider the following two stage differential amplifier: Let's say the input differential voltage is high enough to put the amplifier into saturation region. In that case MOSFET M6 will be pushed to ...
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1 vote
71 views

### Op amp GBW compensation when used in MFB filter

I've been reading through this app note by TI where its proposed that when using a MFB filter a compensation resistor can be added to overcome limitations of lower GBW op amps. I've been working ...
70 views

### Why is the output of the thermistor connected to the inverting terminal of the op-amp in this Texas Instrument IR thermometer schematic?

I am making an IR contactless thermometer by following this application note provided by Texas Instruments. I have some doubts about a few connections in the schematic diagram provided. Vref1 is ...
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2k views

### What does the circuit shown in the picture do?

What does the circuit shown in the picture do? Does it act as a current source? If so, how does this happen?
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116 views

### Purpose of bypass loop heading into analog front-end?

How do the 285k ohm and 4.2 nF components achieve filtering in this diagram? Generally speaking, an RC filter with these values would produce ~133Hz low-pass filtering. Does this still accomplish ...
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### Resistor and Capacitor before Op-amp Follower Circuit

I am still working on a personal project to use an Electrosmith Daisy Seed as a guitar pedal. While doing some research, I came up with my own textbook inverting amplifier setup to take the 10kOhm ...
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82 views

### Is there a single ended input single ended output amplifier integrated circuit?

Yes, nowadays everything is used as operational amplifiers with differential input single ended output , or fully differential output (common mode rejection ratio is high, common mode noise is ...
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1 vote
87 views

### How does this opamp output -4, +4 output?

I'm new to electronics. This circuit is supposed to take 0-2 V MCU signal and convert that to a range of -4 V and +4 V, so when input value changes, the output changes as well till maximum. I think I ...
1 vote
70 views

### Voltage Divider on Op Amp Feedback

I'm trying to understand the schematic of this Adafruit UV sensor: (Note: [U2] GUVA-S125D is a photodiode.) I understand the purpose of the other components, but haven't encountered a voltage divider ...
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### How can I isolate -10 to +10 V using HCNR201 circuit?

See my circuit, it is basically an isolator circuit using HCNR201. This circuit works perfectly with DC 0 to 10 V. But now I want to isolate AC 0 to 10 V. However I have made op amp 4th pin (VEE) ...
1 vote
73 views

### Comparator circuit with rail to rail opamp

In the comparator circuit below, when we select the operational amplifier as "rail to rail input" type, the reference voltage falling on the non-inverting pin is a square wave. Why do we see ...
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49 views

### Testing a Homemade Transimpendence Amplifier

I am trying to build a homemade transimpendence amplifier to measure the signal in a Reverse-Biased photodiode as a laser pulse illuminates it, but am having trouble getting it to actually operate, ...
1 vote
98 views

### Low pass filter with Sallen Key topology

I'm designing a low-pass filter with a passband up to 1 MHz and a stopband starting at 1.8 MHz. I've designed a 4-stage filter using Sallen-Key topology and built it using NE5532P op-amps, supplied ...
59 views

### DC Operating Point simulation of an opamp circuit with ngspice

I'm trying to simulate a linear voltage controlled current source with ngspice and Kicad. This is the minimal circuit I've redrawn for the purposes of simulation. I do want to be able to simulate ...
74 views

### Single ended to differential conversion and back using op-amps

I have a single ended signal that I want to convert to a differential signal. The single ended signal is a 0V - 1.8V rectified signal with a frequency of 16Mhz. To convert the signal a LMH6552 fully ...
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1 vote
69 views

### Calculating Capacitance in a 50 MHz AC Circuit [closed]

I’m working on an RC circuit with a 50 MHz AC signal, a resistor, and a capacitor in series. I’m aiming to determine the capacitance value, which should be between 70 and 400 pF. To achieve this, I ...
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1 vote
130 views

### Determining Op-amp Offset Voltage

Inspired by the video Fake Op-amps from China, I tried to measure the Offset Voltages of my Op-amps using the voltage follower scheme Note that I used a voltage divider (R3 and R4) to create a "...
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51 views

### Signal Amplitude drop due to TVS diodes

I hope you are fine. I have a question. I have generated a 4Vpp signal with a 5MHz frequency using the following sequence: AD9851 (DDS) → AD8001 (Op Amp) → Ferrite bead (2KΩ) → Microfluidic sensor ...
93 views

### I found a simple op-amp circuit online, which confused me

The following circuit is simple. Due to its short output to input, the output will follow the input. Besides that, I would like to understand the op-amp behavior, which is confusing me. As I ...
128 views

### What is causing the spikes at the negative terminal of the opamp in response to the square wave?

I have a simple inverting amplifier as following in which the input is a square wave. By virtual short I expect node VF2 to be at 0V, but when I plot the voltage at VF2 I see spikes that are in sync ...
62 views

### Instrumentation Amp Error Budget... now what?

Bit of a pre-amble before going into the question. I'm working on a project to try and get 100mg worth of resolution out of a 5kg load cell, and I am trying to figure out if my current approach is a ...
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142 views

### What happens when the feedback loop is also connected to the non inverting input in an op-amp

I am trying to understand this tone control circuit in a guitar pedal. The image was taken from https://www.electrosmash.com/tube-screamer-analysis: I do not know how to think about that feedback ...
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594 views

### Differential vs. Single-Ended amplification for sensor sampling

I'm designing a load cell amplifier that should be low-cost, and functional in a noisy environment. The load cell is a 1k balanced full-bridge on a single package. The read speed requirement is only ...
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### LT6268-10 OpAmp Noise

Following on from my previous post , I printed the circuit as below however getting very noisy signal. what am I doing wrong here?
213 views

### LT6268-10 Opamp Oscillation and Offset

Below is my Photodiode-OpAmp circuit that is configured as Transimpedance Amplifier. When I put both inverting and non inverting into ground, no signal is coming out. However when I connect ...
1 vote
132 views

### Op-Amp for microelectrodes in PBS conductive solution

I am using micro electrodes in a conductive solution (PBS: Phosphate Buffered Saline) and I would like to be able to measure the voltage with a National Instrument measuring device (PXIe6345). I apply ...
1 vote
43 views

### How to set a timer for this circuit?

I have this circuit however I need to make a timer that works for 2 - 2.30 hours, so I have this circuit here: But I need to know how much should R1 and C1 be approximately to fulfill this job? Note: ...
53 views

### Need help opamp or optocoupler?

What is the best route? Optocoupler or opamp (if opamp, which one?) I need to reduce this 5.8V pulse generator to 0.84V Have an automotive application I am trying to find a solution. Basically I want ...
366 views

### Constant volatge at the output of LM311

I made a PCB based on the following schematic. The inputs of the comparator work as expected (i.e., the capacitor voltage or the voltage at the non-inverting pin gradually increases and, after a few ...
32 views

### Strange asymmetric saturation with ADA4099

Good afternoon — my first question here, I hope I follow all the rules... So, I am trying to design a series of filters with op-amps that have a shutdown pin, using only 0 ­→ 3.3V supply and an analog ...
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### What type of amplifier circuit do I need to drive a piezoelectric ultrasound transducer?

I would like to drive the following piezoelectric transducers at 200 V or their maximum voltage (60-1000 V): https://www.manorshi.com/16mm-Dog-Repellent-Ultrasonic-Transducer-25khz-Detect-Sensor-...
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86 views

### TL072CP non inverting circuit doesn't amplify

I am using TL072CP op amp in inverting mode to amplify guitar signal. This is the circuit I have made: I assembled it and even when changing resistors of different values and trying out different ...
1 vote
60 views

### How to simulate for the Gain of opamp Bridge Differential Amplifier?

Hi experts, I have this circuit, with a bridge connected to an op-amp in differential form, and I want to simulate it for the Gain of the circuit in PSPICE. I have found it's gain by hand, which comes ...
54 views

### Audio Codec Input/Output Channel Stages

I am planning to build a PCB for a Eurorack Modular Synthesizer, incorporating an STM32 for DSP and a bidirectional Audio Codec like the TLV320AIC3104 to handle the ADC/DAC. Eurorack audio signals ...
984 views

### Infinite output impedance in amplifier, instead of 0?

The question asks: "Exercise 14.5 Assume an ideal op amp and use the summing-point constraint to find an expression for the output current io in the circuit of Figure 14.14. Also find the input ...
60 views

### Applying KVL in op amp with floating source

From my understanding, the solution first applies the summing point constraint even though there is no ground on the non-inverting input, leading to 0V on both inputs. But how do they apply KVL across ...
327 views

### Is it correct to apply KVL through the 2 inputs of an op amp?

The question asks; "P14.25 Analyze each of the ideal-op-amp circuits shown in Figure P14.25 to find expressions for 𝑖𝑜. The top part is the question, the bottom is the solution from the ...
223 views

### How are opamp node voltages being set in the following circuit and what is the use of the diode configuration?

I am using a PCB which has the following opamp configuration implemented. It's supposed to be a precision buffer for the source V3. I accidentally connected the source V4 as well and observed strange ...
500 views

### Issues with ICL7660 ICs from eBay - Overheating and Failure

I recently purchased several cheap ICL7660 ICs from eBay to use in an OpAmp circuit. Unfortunately, I've encountered issues with these components, specifically overheating and subsequent failure. Here ...
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### What is the maximum dBu I can send into a microphone input in this schematic?

The schematic below is from the Icom 9700 radio service manual (page 80). I would like to feed this input from a mixer board's ALT-3/4 outputs, and I want to avoid blowing the TS462 microphone preamp ...
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### Part name of this IC - "LLA#537"

I want to know the part numbers of the components marked as shown in the attached image.
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### Part name of this IC - Analog Devices, 8-pin, "S 6B" A 06" "C 42"

I want to know the part numbers of the components marked as shown in the attached image.
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