# 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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### Differential pair with active load including resistance [closed]

In solving the differential pair with an active load, I am able to find the gain without including R1 as shown in the figure. When R1 is included, I am stuck on how to proceed. Could you help me out?
42 views

### DC offset of DC signal with op-amp

I have a DC signal from a DAC in the range of [0:3,3]V and want to convert it to be in the range [-5:5]V. My approach would be to scale with op-amp with gain 3 and then DC offset. I've read that this ...
69 views

### Op-amp voltage comparator

I am using an op-amp (LF353P) for my voltage comparator circuit. The supply voltage for the op-amp is +12 V and -12 V. The input voltage for the inverting pin (Vref) is 1.1 V. The input voltage for ...
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82 views

### Rescaling voltage input

Measuring laser transmission with photodetector, I obtain voltage values in the range of [0:9]V. The output of the photodetector is to be observed on oscilloscope and taken as input in ADC of Arduino ...
73 views

### Does op-amp virtual ground only apply in steady-state?

Does op-amp virtual ground principle only apply in steady-state? Assuming a negative feedback config of course.
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### Does op-amp virtual ground hold in open-loop config?

An op-amp is defined by the following equation $$Vo = A(Vp - Vn)$$ Rearranging, $$Vp-Vn = Vo/A$$ A real op-amp will have a gain around 100 and the output will be limited by the supply voltage say ...
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18 views

### Instrumentation Amplifier Simulation INA122P Output Voltage not zero (TINA-TI)

I have the following circuit, the INA122 instrumental amplifier. when RG pins are not connected, the default gain is 5. I am sure that the bridge is balanced, however, for the simulations, why there ...
1 vote
36 views

### How to control high current voltage with small current voltage linearly?

I want to make an 18650 charger without a microcontroller for fun, I was designing a very simple circuit but I had a problem with adjusting the voltage if current/voltage excceds max current/voltage. ...
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100 views

### How to improve this precision rectifier by further decreasing cross-over transition times?

The Circuit The rectifier comes from TI's TIDU030: Precision Full-Wave Rectifier, Dual-Supply application note. My "benchmark" used as a baseline for evaluation is as shown below, powered ...
231 views

### How to add gain to this op-amp based precision full wave rectifier?

The design for the rectifier is rather clever, and comes from TI's TIDU030: Precision Full-Wave Rectifier, Dual-Supply. It looks as follows: simulate this circuit – Schematic created using ...
39 views

### OPA548 not generating correct output pulse

I have created a circuit for which I would like a rail to rail output of 0 - 15V, using an OPA548 with the driving waveform generated by a microcontroller DAC powered by 3.3V. The datasheet for OPA548 ...
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70 views

### Why is my oscillator way too different from simulation results?

How's going dear engineers. I hope your everything's going well. I've made a sawtooth waveform oscillator aim for about few hundread kHz. I didn't see any problems on simulation results, everything ...
1 vote
24 views

### Measuring current of GUVV-C20SD diode with transimpedance amplifier

My goal is to measure the UV light using this UV diode and a trans-impedance amplifier, but I need help with the understanding of similar circuits. I have checked out the following image and I don’t ...
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271 views

### Op-amp integrator gain from calculation doesn't correspond with real-world measurement

In my integrator circuit, I added one feedback resistor R2 and one bias compensation resistor R3. The values of the components are values I have measured before I applied them on this PCB Evaluation ...
• 43
72 views

### Instrumentation amplifier cross-connection circuit

I am trying to implement a circuit from an ADI app note that I have not seen anywhere else : Here it is in PDF format which is a copy of this article. I strongly encourage reading it as it is quite ...
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70 views

### Calculated crossover frequency of Op Amp integrator doesn't match the simulation

I am calculated the crossover frequency of my integrator circuit with the following formula. $f_{0\text{ dB}} = \frac{1}{2\pi R_1 C_1} \approx \underline{\underline{154\text{ Hz}}}$ Unhappily, the ...
• 43
44 views

### Help designing a 3-phase inverter [closed]

I was tasked with designing a simple-ish 3-phase inverter circuit, but I am not quite sure where to start. My first thought was to phase shift the pulse from a 555 timer using something like this: ...
431 views

### Op-amp simulation

I am not sure what's the mistake I am making in the below simulation. Below is an MCP660 non-inverting op-amp with a gain of 3. Case1: Input: 1 MHz; Offset: 0.5 V; Pk-pk amplitude: 0.2 V Result: The ...
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218 views

### Possible causes of ceramic capacitor damage on high-voltage op-amp supply pin

I am working on a waveform generation board. The board contains +-200 V supplies and +-24 V supplies. The board takes a low voltage (+-15 V) waveform from a DAC on separate board and outputs +-200 V ...
• 69
645 views

### Photodiode speed limitation

I have a system which demands optical data transmission since rotating parts are present. A mixed mechanical-electrical engineering project has led us to use photodiodes to receive data from one ...
• 1,126
50 views

### Adding current follower in the circuit: error [closed]

I have the below circuit and when I add the current follower op-amp circuit it doesn't work. When I add an ideal op-amp it works, but when changing it to a realistic op-amp it doesn't. What could be ...
161 views

### Op-amp gain not working as expected

I'm trying to amplify a really small (1.3 mV) voltage from a sense resistor. I am using the following schematic: My load is an LED and resistor. For R2, I'm using a 470 kΩ resistor. For R1, I'm using ...
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62 views

### How did they consider $I_{3_{min}}$ and $I_{3_{max}}$ in 4-20 mA current transmitter? [closed]

Define the minimum and maximum currents through R3. See Design Note #5 before defining these currents. For this design, $I_{3_{min}}$ = 20 μA, $I_{3_{max}}$ = 100 μA are chosen. This link has the ...
121 views

### Simulating voltage divider?

Over the past weeks, I've been looking into an analog method of dividing 2 voltages such that V1/V2=Vout. I found many sources on Google using methods like log and antilog amplifiers or a multiplier, ...
1 vote
56 views

### Why is Hf negative while Vf is positive? Aren't they the same but without Vin?

For the inverting op amp, I've seen the equation Vout/Vin = Hf/Hr Hr is the same as Vr but without Vout. Why isn't Hf the same as Vf but without Vin? What I mean is that Vr = Vout[R1/(R1+R2)] and Hr = ...
45 views

### Op-amp non-linear Bode plot

The figure below is an op- amp's Bode plot. In the ideal situation, there are no fp1 and fp2 in there. I would like to know why the real op-amp will have these two poles. Is there any document I can ...
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### How does feedback factor works in equation V-/Vout [duplicate]

I am asking this question to understand this. It states that V-/Vout is equal R1/(R1+R2) Here : V- is equal 0V. Because V+ is grounded. So V-/Vout = R1/(R1+R2) => V- = Vout*R1/(R1+R2). But V- is ...
56 views

### What is the feedback factor in the inverting Op Amp?

I've got a question about feedback factor. Because I don't know how to calculate it. I've been talking with some people and they say that feedback factor here is equal -R1/R2. Which is the reverse of ...
1 vote
98 views

### Buck converter adjustable output-voltage using digital potentiometer [closed]

I am trying to design a buck converter using an LM2576HV (Vref: 1.23 V) and a digital potentiometer (input: 48 V, output: 0 to 48 V, Imax= 3 A). The digital potentiometer with the highest supply ...
1 vote
44 views

### Asking experience for this flow-through pressure sensor: 26PCAFG6G - Honeywell

I have the following sensor:26PCAFG6G The output of the signal is a differential output from a Wheatstone bridge with 0 - 1 psi, or 0 - 70.3 cmH20 corresponding to 0 - 16.7 mV, I am using AD623AN for ...
1 vote
51 views

### Does increasing gain of an op-amp improve transient response speed?

Consider a simple op-amp in a feedback configuration. You can consider the op-amp to be dominant pole compensated and approximated as a first order system. Let's say that the transient performance (...
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### Is a buffer stage needed in this signal chain?

I am designing a signal chain that includes a 4 pole cascade Sallen-Key filter based on the AD8034. The circuit will be used to shape tail pulses (~10ns rise time, ~50us decay) into gaussians. The ...
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43 views

### Operational amplifier controlled LED voltage (power supply)

I am trying to use two APEX PA12A to control two groups of IR LEDs. I have this circuit: PA12A to take the PWM 0-5 V control signal to limit the power supply to LEDs. The thing is even when the PWM ...
89 views

### Is this cascoded opamp structure unstable by design (LTspice)?

I am playing with a cascode op-amp design and I have problems judging its stability (schematic at the end of the post). When I judge the DC or AC analyses, it all looks good. No peaking and good phase ...
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### Adjusting output voltage feedback with a Howland Current Pump

I'm designing a variable bench power supply using the LT3790 IC. My requirements were adjustable from 1 V to 24 V in 10 mV steps, and a current limit adjustable from .05 to 5 A in steps of 5 mA. I ...
103 views

### Why is this op-amp outputting such low voltage?

Why am I not getting the expected gain out of my op-amp? I m using a 16-pin TI OPA4322SAIPW op-amp with a Advanced Photonix 019-141-411-R photodiode and this circuit: where Rin is 1.8 kΩ and Rf is 27 ...
83 views

### Need help to understand op-amp input resistor and capacitor network

I'm trying to understand the circuit design from this application note. Here is the figure: The author said: Resistor RIN provides a dc return path for the VS/2 reference voltage and sets the ...
42 views

### Current mirroring in diff amplifier

Hi , I tried to design simple current mirror (load) based differential amplifier. I was trying to make it for optimum swing limit. In the first image as you see I used an ideal current source . I was ...
1 vote
198 views

### How to calculate op-amp circuit when there are two feedbacks?

I've got a question: how should I solve this? I've seen a thread were it was solved, but I don't know why the V+ is equal = V+ = Vout+(Vin−Vout)*R/(R+Rs) Like here: How are positive and negative ...
34 views

### Why does PMIC temperature increase drastically when opamp gain is increased?

I have an RF signal conditioning circuit that uses two AD8065 opamps for coarse gain. The board is powered via +/-12V, and is stepped down to +/-6V using MC7906 and MC7806 PMIC. The gain is controlled ...
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### Analog signal conditioning circuit selection for STM32F2 microcontroller ADC inputs

This is my first time designing an analog signal conditioning circuit for ADC inputs. The card will have up to eight analog inputs connected to eight STM32F207ZG ADC channels (stm32 mcu datasheet). ...
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1 vote
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### Eddy-current input to op-amp misses reading at times

The problem is only in the input stage of the op-amp. Edited: removed reference to "eddy-current" and changed to "reluctance". The reluctance-current is generated from two coils by ...
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### Feedback capacitor vs Miller capacitor in discrete op amp circuits

This is an overly simplified operational amplifier circuit with a feedback applied. The common way to make it stable is to add a dominant pole to the transfer function usually in a form of a Miller ...
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### Help understanding TL082 pre-amp/tone circuit

I am trying to construct a small 5W guitar amplifier with tone control as an introduction to audio electronics. I have taken two openly available circuits and I am trying to reverse engineer and ...
50 views

### Cascading opamps to drive a MOSFET [closed]

I suppose, this is a continuation of this question: Parallelizing opamps for higher precision For the moment I'm leaning towards cascading opamps by implementing a Composite Amplifier, albeit a lazy ...
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### Compare same signal with different voltage thresholds using op amps [closed]

I would like to use two op amps to drive a transistor when receiving two different voltage ranges from the same input signal for a project. For example, I would like to switch the transistor on when ...
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### Slow slew-rate compared to the datasheet

I'm trying to create a 10 kHz PWM signal through use of op amps. In the output I'm using a TLV272IP op-amp working as a comparator: Since it has as slew rate of at least 1.8 V/us this should give a ...
52 views

### Impedance of buffered LC filters?

I am wondering if its possible to buffer LC filters? I am also wondering about the I/O impedance of the LC filters if you can buffer them. I do know the component values you pick for the LC filters is ...