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Questions tagged [instrumentation-amplifier]

An instrumentation amplifier (InAmp) is an integrated circuit or operational amplifier topology that has high input impedance differential inputs and a low impedance single-sided output. Because of precision laser-trimming techniques for passive circuit elements, InAmps implemented as integrated circuits can achieve impressive common mode rejection ratios, while discrete OpAmp implementations can be disappointing in this regard.

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Cascading Op Amps for Phototransistor Output Conditioning

I am working on a project in which I am using an IR phototransistor to detect changing low levels of light. Currently with very high load resistance I can get a reading of 40-60 mV but I would like to ...
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60 views

Interfacing instrumentation amplifier

I would like to interface several LTC6915 instrumentation amplifiers with a microcontroller. I have a schematic which looks something like below image: What I figured out is that the two amplifiers ...
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55 views

How to approach the SNR needed for this electronic instrumentation

I have an issue with using concept of SNR in many instrumentation. To ask the question more clear, I want to go with a particular example. Let's say a Wheatstone bridge type 500N nominal force ...
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What is the difference between input and output offset voltage for an opamp?

Looking at many OpAmp (and InAmp) datasheets, I find the info either confusing or lacking. For example, in one datasheet they just call something Offset Voltage ...
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83 views

AD620 pH probe has a positive voltage offset!

I am a chem eng. but little background in electronics. I'd like to interface a pH probe with an AD620A, the original PCB that came with pH probe was damaged by a current leak in the solution. I made ...
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89 views

Logarithmic amplifier with high slew rate — mutually exclusive?

Does anyone know if the basic construction of a log amp (with a diode or BJT providing feedback from output to input) is in conflict with any ability to reach high slew rates? I've been looking (...
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39 views

Instrumentation Amplifier Saturation to Rails

I am working with a TI INA821 Instrumentation Amplifier to try to amplifier a 0-5mV (delta) analog signal off a strain gauge. To reiterate, every DC analog value between the delta of 5mV represents a ...
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54 views

Noise mitigation in +/-5mV instrumentation amplifier?

I am building a differential amplifier to boost a 0-5mV (delta) signal off a load cell wheatstone bridge. In simulation, the design works here (falstad): (for those who have not used falstad circuit ...
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51 views

NTC Project (Wheatstone Bridge + Instrumentation Amplifier) - Stuck!

I've been lurking through these forums for years but just now had the urge to ask for help. I'm creating a thermometer (using an NTC thermistor) for my college project. I began to analyze my sensor ...
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134 views

Strain gauge amplifier - so much noise!

I'd like to use atmega328p to read force with strain gauge. I'm using one 1k strain gauge and 3x 1k ohms dummy resistors. My circuit looks like that: I'm using DAC to remove offset from bridge. As ...
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49 views

Remove bridge offset before ICF amplifier or at FB pin?

I'm making project where I would like to read from stain gauge sensor. It will use only one 1k ohm (or 350 ohm) strain gauge and 3 dummy resistors to complete bridge (1k or 348 ohm). I'd lik to feed ...
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49 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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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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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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5answers
232 views

Instrumentation Amplifier required for 24 bit ADC?

I am trying to build a measurement circuit that is capable of measuring voltage signals in the order of micro volts. Signal Characteristics: Voltage: Anywhere between 1 uV to 100 uV Frequency: ...
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81 views

What is role of R9 resistor at input to OPAMP in this circuit?

I guess it has to something with offset nulling but not getting how .Circuit shown is of instrumentation amplifier.
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ADC sensing Range of MSP430I2020 controller

my project is based on Weight scaling using load cell. currently, I'm working on inbuilt 24 bit ADC of msp430i2020 controller.internal ADC reference voltage is 1.2 volt. Capacity of load cell -300KG ...
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Amplification problem

I am using an instrumentation amplifier AD620ANalong with another amplifier TL084CN in series. Both have gains of 100 which essential for me since the input is in microvolt range. The frequency is 87 ...
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55 views

Characterization of an Amplification/ADC circuit

I build a small amplification circuit in order to amplify the low voltage signals of my passive sensors (the sensors have a source impedance of about 50-200 Ohm and they output a low voltage signal in ...
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Voltage conversion between multiple orders [duplicate]

I have this circuit in which I want to convert the input voltage of micro order to volt. The circuit image has been posted. I have figured out the bandpass filter ( basically everything after the big ...
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183 views

Conversion from microvolt to volt [closed]

I have a circuit which has an input of voltage of the order of micro. I want to convert it into volt order. I am using an instrumentation amplifier AD620 with gain of 1000 to first convert it into ...
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95 views

What connector is this? I haven't a clue, looks standard though

https://imgur.com/a/D4sBi3D I need to get an adapter to connect the plug from the green board, to the plug on the brown board. However, I have no idea what the green board's connector is called, so I ...
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97 views

Analog switch on an instrumentation amplifier input

I'm working on a project for school that involves a configurable input stage (AC/DC coupling and variable input impedance) connected to an instrumentation amplifier. I am wondering whether I will ...
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Buffering Vref on AD623

I am measuring AC signal using an instrument amplifier AD623. This will be fed to an ADC in the 0/+5V range. Therefore the signal must be centred on 2.5V. A voltage divider will create the 2.5V using ...
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Variance in ECG lead resistance ; its effect ; CMRR

We are designing custom ECG electrode with flexible printed wires as to reduce wires clutter from different electrode. The manufacturer has made the patch but the resistance variation between all the ...
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767 views

Circuit for small level voltage detection (microvolts)

I have been working on a project lately which help in the detection myogenic potentials (of the levels of micro-volts). After studying from several places, I finalized the following test circuit. The ...
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Creating an Input bias current return path (for an amplification circuit)

I have passive sensors (pyranometers that consist of thermopiles and measure sun irradiation, sensor specs are attached at the bottom of this question) that output a low voltage signal so I need to ...
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664 views

RC Lowpass Filter between Amplifier and ADC input

I have sensors (pyranometers that consist of thermopiles and measure sun irradiation) that ouput a low voltage signal so I need to amplify them using an instrumentation amplifier. I have chosen the ...
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Gain bandwidth product of amplifier in a DC scenario

I think I have a simple (but still to me confusing) question regarding the gain bandwidth product (GBP) of an instrumentation amplifier: Datasheet (AD8237) I have sensors that change their output ...
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Signal response and settling time graph analysis

I have come across a datasheet of an instrumentation amplifier. I have a difficulty in understanding the signal response vs settling time graphs. Can someone please explain figure 28(page 10) of the ...
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79 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
440 views

How to make repeatable Op-amp amplifier circuit

I did a simple op-amp based 100X gain single ended circuit. I tried to order 100 IC's and manufactured them. But found that out of 100 only 60 devices have same and expected baseline. What could be ...
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1answer
141 views

Amplifier with true ground output swing and A/D conversion

I want to amplify a 0-20mV signal from a sensor to 0-2.048V in order to feed it to an ADC (with a reference voltage of 2.048V). After I will input the digital signal to a microcontroller. I need to be ...
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692 views

What is the purpose of op-amp in the output of Instrumentation amplifier

I encountered a problem while solving an analog circuit. I just need to know the purpose of the last op-amp (K4) at this circuit: while solving I understand it just amplify the output voltage from ...
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Mathematical model for differential signals and relation with reality

i have a question and i hope is not that strange. i spend some time asking myself how people came out with the mathematical model for differential signals and why is this better in this way?! to be ...
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2answers
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How do I keep this VCCS stable?

I have designed a circuit to measure impedance of certain tissues. It injects a constant current from two electrodes and measures the voltage at different electrodes. The system mainly consists of a ...
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1answer
64 views

Effect of changing current sense resistor value in amplifier circuit

I am trying to implement a current output amplifier circuit shown below. Current is measured across sense resistor Rs to adjust input voltage Vin. Gain: G = -Iout/Vin = R2/(Gain-of-IA1*R1*RS) The ...
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Building circuit to amplify small sensor signals using an Instrumentation Amplifier and 24-Bit ADC

I'm a beginner when it comes to circuit design and I have spent the last few weeks doing research on this topic. I have now chosen some ICs (Instrumentation Amplifier and ADC) and would like to build ...
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1answer
44 views

Calculating drift/precision on a temperature circuit

I'm hoping to get some guidance with a circuit I designed. I have a current source which operates between 200uA and 400uA. In order to measure it, I used the following circuit before feeding it into ...
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2answers
132 views

ECG electric design: 1 and 3 op-amp designs from a safety point of view

During the design of an ECG using an instrumentation and a differential amplifier, we can across this question: Comparing the one and three op-amp designs from a safety point of view: of the two ...
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Improve a ECG I am using an instrumentation amplifier

I am doing an EMG as a part of my senior design project. I am currently using an Instrumentation amplifier but my professor suggested using a driven right-leg circuit. I was wondering how using a ...
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751 views

How to determine op-amp gain with active feedback?

The Howland current pump uses an op-amp in the configuration below with a resistive feedback network which gives me the gain show below: But if I decide to swap the feedback resistor for an ...
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67 views

Measurement of high voltage with low voltage circuit

Is it possible to make a high-impedance, precision measurement of a 10V DC signal (dynamic range requirement is only ±1V with a DC-1kHz BW) using amplifiers and an Sigma-Delta ADC supplied only by +3....
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101 views

How does common mode range include the negative rail?

How do the devices like AD8220 handle the common mode voltage equal to the negative rail or even lower voltage (Take a look at figure 30 of AD8220 datasheet) ? Does the operation of the amplifier ...
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1answer
429 views

Is there any difference between AD620 vs INA128?

I'm trying to make an EMG sensor. I've found some tutorials, for example, DIY muscle sensor/EMG circuit for a microcontroller, but my main question is can I make an EMG sensor using AD620 instead of ...
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1answer
38 views

Spice model for analog devices instrumentation amplifier giving unexpected outputs

I'm trying to do noise analysis with the AD8421 (although the specific in-amp doesn't matter). Right now I have two time dependent voltage sources on the inputs of the amplifier and the output seems ...
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3answers
160 views

Why do tube amplifiers have such (relatively) small reservior capacitors?

In learning about guitar amps, I've been studying the schematics for solid state and tube amplifiers, and I found a pattern that I've never seen an explanation for. If you consider any of the main ...
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228 views

AD620 instrumentation amplifier with Wheatstone Bridge-based KMZ10B sensor

I would like to ask for help regarding a certain phenomenon related to amplification by the Analog Devices AD620 instrumentation amplifier (device home page, device datasheet). Vcc is 5V. The AD620 ...
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27 views

Diifference between INA827AIDGK & INA827AIDGKR

Whats the difference between the same package of the IC INA827 - INA827AIDGK vs INA827AIDGKR? The datasheet makes no mention of any differences. Except in in.element14.com where INA827AIDGK is ...
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Why are two stages used for an instrumentation amplifier?

When we have a two-stage instrumentation amplifier, such as the following. Why do we need the first stage of the two Operational Amplifiers? Couldn't we just input V1 and V2 into the differential ...