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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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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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190 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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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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54 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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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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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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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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47 views

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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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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601 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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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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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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138 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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691 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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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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53 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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38 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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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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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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60 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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86 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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265 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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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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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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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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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 ...
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188 views

Instrumentation amplifier output stuck high

I tried to design an inamp for a K-type thermocouple. In theory the gain of this amp should be 250 (close enough to 10 mV/K), and if my understanding of instrumentation amplifiers is correct the ...
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174 views

Why does an Instrumentation Amplifier need a reference?

I am working with the INA826EVM board and I am wondering why it needs an additional op-amp for a reference in the Instrumentation Amplifier?
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Why CMRR degrades in instrumenation amplifier?

Why CMRR degrades in instrumentation amplifier when R3 (only the feedback resistor) is increased keeping all other resistances constant at a fixed value? What mathematical relationship links R3 and ...
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145 views

Create small variations in voltage for opamp reference pin

Hello and thanks beforehand. I'm designing a circuit to measure 4 wheatstone bridges using 4 Analog Devices AD8422 in-amps. Now, i'm feeding the AD8422 output to a 3.3V ADC, so i'm offsetting the ...
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LTspice simulation of AD8421 instrumentation amplifier giving incorrect output voltages

I am trying to run a simple simulation of an instrumentation amplifier (AD8421, model from here) running on a single supply, but the output does not seem to be correct. The screenshot below shows the ...
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Maximum Gain For Chopper Stabilized Instrumentation Amp (MCP6N11)

I am using a Microchip MCP6N11 chopper stabilized instrumentation amplifier to amplify the signal from a MPX2300DT1 Wheatstone bridge pressure sensor. My schematic is attached. As shown the gain is ...
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Noisy amplification and low light: photodiode and op-amps question

My formal education was in mechanical engineering and I’m well trained in some CS as well. Yet here I am on an electrical project (that will eventually turn CS). I have been lost and confused for many ...
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195 views

Art of Electronics figure 5.87 (revised)

The circuit below comes from the errata of The Art of Electronics. Why is the circuit in Figure 5.87-B (bottom) correct? As drawn, 50 mA at output will mean -5V at the inverting input of the Op-Amp. ...
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238 views

high input impedance circuits

Working with circuits to get high input impedance. This is to capture signals while introducing as little interference as possible to the preexisting circuit, to load the source as little as possible. ...
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166 views

Instrumentation Amplifier input saturation problem

I designed and ordered some PCBs for in-amp but having a problem, I think it is input saturation. The power supply is 0V, 6V, and 12V rather than -6V, 0V, 6V but I am only interested in AC so this is ...
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Effects of increasing current on external noise and SNR for analog transmission

This is a conceptual question about long analog signal transmission exposed to capacitive coupling and EMI noise as shown in below figures: simulate this circuit – Schematic created using ...