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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2answers
73 views

How to design two circuits with Instrumentation Amplifier to produce the same output?

I want to measure the current in a 5V circuit. The current is between 50uA and 2.5mA. The current is from a NTC and it changes slowly (10Hz measurement is fast enough). Here is the typical ...
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50 views

AD620 reference terminal problem

I'm trying to add a DC offset level to a sine signal through an instrumentation amplifier (as the figure below shows.) The problem is that, in the simulation, everything works perfectly, however, in ...
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Hall Effect Shielding

The objective of the circuit below is to get the difference of the hall effect output and a 1 volt reference, then amplify it. When I first built the sensor and tested it, it worked very well. This is ...
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165 views

Instrumentation Amplifier - circuit analyze

I found this schematic in LT1014 datasheet: What the pointed op amp (and the circuitry around it) is for and how it works? Why do we need to cancel the bias current? What's the application for such a ...
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81 views

AD620 Instrumentation Amp EMG circuit [duplicate]

I was looking at the datasheet of AD620 instrumentation amplifier. It had a circuit for measurement of EMG signals. The gain of 7, as written on the amplifier, is justified for this amplifier ...
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45 views

Sampling Capacitor In INA

I am looking at parts like the LTC2053 which use a sampling capacitor on their input. I had a few questions: Does the input impedance of this amplifier simply look like the sampling capacitor (1000pF)...
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18 views

Higher gain at higher frequency in instrumental amplifiers

I am using an instrumentation amplifiers (INA181). When the gain (G) is set to 10000 the behavior is as expected. However, when G is set to 1k there is an increase in the output signal going with the ...
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34 views

Cascading two instrumentation amplifiers to achieve higher gain

Is it possible to cascade two instrumentation amplifiers (for instance INA128)? let's say each has a gain (G) of 100 up to 100 kHz. Would this result in a G=10k up to the same frequency?
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35 views

Calculate the differential common-mode gain of instrumentation amplifier

I am trying to design an instrumentation amplifier with a CMRR of 50 dB. I have to target a differential gain of 60 dB. $$ CMRR(dB) = 50 dB = 20log(\frac{A_{vd1}}{A_{cm1}})+ 20log(\frac{A_{vd2}}{A_{...
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19 views

why is the reference of strain gauge changed depending on gains of amp? use ina128 and ad8542

I made a circuit for a load cell. It is available but when it is applied to the strain gauge, it has a problem. Reference voltage : 1.65 V When I measured value of load cell, I can see the change ...
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1answer
41 views

Servo drive in biopotential amplifier

I have to design a bio potential measurement system: AD converter and the connecting digital / software part an analog amplifier stage: basically a regular ECG amplifier composed of discrete ...
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97 views

What actually is the differential gain of an operational amplifier and why does its value change when we consider the common-mode gain?

Okay, this may be a stupid question, but at the beginning of my Applied Electronics course they taught us that the differential gain \$A_d\$ of an operational amplifier is ideally infinite; however, ...
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84 views

C0G vs polypropylene capacitors in signal filtering

Can anybody give me a comprehensive pros and cons list or explanation about the differences between C0G (NP0) ceramic and polypropylene capacitors? I would like to use them in signal filtering and ...
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Self Oscillating INA with Multiple Feedback filter

I'm working on a circuit to receive a signal in the 220Hz range. The signal is created from a small loop transmitter emitting a 50% duty cycle DC square wave of about 4.8 Watts. The receiver is a ...
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32 views

INA125 problems

I'm trying to measure a bridge sensor using an INA125 connected to my Arduino and Adafruit ads1115, but the output seems stuck on 5.88V (the power supply is 12V singl supply). Its connected as in the ...
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53 views

Operational Amplifier and Strain Gauge

My laboratory involves using a strain gauge and an instrumentation amplifier to amplify the signal from the strain gauge. The op amp schematic is shown below: Any assistance with the following ...
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1answer
34 views

XADC Current Sensing Reference Design

Please refer to this reference design for AC701 (snippet below). The schematics, specifically the current sensing sections in pages 34-36, show this: I want to understand why, for the REF output of ...
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32 views

INA125 gain problems

I'm trying to use an INA125 to read a load cell. Its connected as in the single supply diagram in the datasheet (see below). The gain should be 4+60K/Rg. However whatever resistance I make Rg, the ...
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36 views

Thermocouple chip & CJC compensation under 0°C

We are currently designing a "conditioning" module that takes a couple of sensors (T°, Pressure but also via digital bus) and repeats over CAN / also outputs them in nice and clean analog signals (0-...
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291 views

K-Type Thermocouple, Instrumentation Op-Amp and Arduino

I am Trying to read in a K-Type Thermocouple to a 0-5V Arduino Uno. I Can read my Thermocouple directly using a Fluke meter on temperature setting giving me the correct value of 21°C, but when I ...
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696 views

Not understanding how the gain works in the 1st stage of an instrumentation amplifier

For the following instrumentation amplifier, I am having some confusion understanding the gain process for the 1st stage. I understand that the 2 input amps are essentially 2 non-inverting amplifiers ...
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1answer
104 views

Why is a Instrumentation Amplifier Necessary for A Wheatstone Bridge (small signal circuits)

I do not understand why an Instrumentation Amplifier is Necessary for small differential signals? Why is it necessary that the initial inputs to the amplifier must be high impedance from the ...
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109 views

Why is an Instrumentation Amplifier Used Over a Standard Differential Amplifier? [duplicate]

I am having a bit of a hard time understanding why instrumentation amps are used over a single differential amp? For example, the differential signal that I have is very small and comes from a ...
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77 views

instrumentation amplifier with [2 opamp + ADC] vs [3 opamp + ADC]

I have an 16bit ADC able to do differential measurement with range -5V to +5V (ADS1115), do you think both circuits would work? It's required that the adc input is within -5V and +5V range, else it ...
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70 views

Why choose to tie the output to the non-inverting input of an op-amp?

I came across this schematic design of a driven-leg circuit, designed in order to enhance the performance of an ECG amplifier. As far as i can see, the solution provided here is a little bit ...
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2answers
83 views

Op-amp output wanders over the course of a few seconds

In one of our designs we are doing signal conditioning of a load cell (Wheatstone bridge) We have an issue where the main instrumentation amplifier an AD8224 has an output signal that wanders by ...
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180 views

Working of INA826 instrumentation amplifier for Pt100 RTD

The schematic below contains an INA826 used to amplify the resistance of the Pt100 RTD across J1. Gain is set to 10 through the 5.49K ohm resistor. Is this ciruit amplifying only the voltage across ...
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169 views

Can I use a simple voltage divider with an instrumentation amplifier to measure from 0 to 10V?

There is a design of a circuit proposed in the following way: simulate this circuit – Schematic created using CircuitLab The amplifier has a gain of 80, on R1 when the input voltage is equal ...
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1answer
90 views

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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1answer
61 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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61 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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2answers
127 views

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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158 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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1answer
103 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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75 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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71 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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1answer
131 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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1answer
187 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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1answer
70 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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1answer
57 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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154 views

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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2answers
129 views

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
332 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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102 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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31 views

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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56 views

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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1answer
72 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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25 views

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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3answers
400 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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1answer
104 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 ...