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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Do you have to use an instrumentation amplifier to measure voltage across a 0.01 ohm shunt?

I was planning on implementing a current sense feature on the STM32 Bluepill to measure the current output of a solar panel (150 mA short-circuit current, 14 V Open-circuit voltage) using LM358 ...
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1answer
71 views

Oxygen sensor voltage changes when machine is powered on. Interference?

I built an Arduino Uno based control panel for an altitude training machine, which connects to an oxygen sensor. The value is amplified by an instrumentation amp (INA122P) and read into the analog ...
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2answers
36 views

Read three signals from MPX2102DP pressure sensor

I have an MPX2102DP pressure sensor. I have designed a simple instrumentation amplifier using the OP07 amplifier to read the output (differential pressure) of this sensor. From the datasheet, I have ...
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1answer
57 views

Common mode rejection range for INA122

I am fairly new to electronics and I am encountering some issues in using the INA122 instrumental amplifier. I am using it as in Figure 3 in the spec sheet for the device https://www.ti.com/product/...
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1answer
70 views

Why is the noise gain these opamps 500? I feel it should be 250

I wanted to check the bandwidth of the first stage of an instrumentation amplifier configuration and this is the circuit: Since, the noise gain of an opamp is (1+Rf/R1), for each of the op-amps the ...
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3answers
75 views

Help identify ECG signal acquisition using AD2

I have recently got into electronics. I have access to an Analog Discovery 2 (AD2) kit with signal generator and oscilloscope functions. I have been trying to teach myself how to use this equipment ...
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1answer
36 views

Can someone help me understand why in this datasheet the Vcm vs Vout curve(or the 'diamond curve') is specified for 'all gains'?

From what I read so far and from the equations used for deriving the diamond plot for instrumentation amplifier, the shape of the plot changes with gain. Following is an example: However, in the ...
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1answer
55 views

Why is the Wheatstone bridge configuration almost always used for sensors over a simple voltage divider? [duplicate]

Everywhere it seems to be taken for granted that a Wheatstone bridge is more precise, accurate etc. I don't see why it would be any better than a voltage divider if I am directly measuring the voltage ...
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72 views

Can someone help me understand why exactly high CMRR is so important, particularly in medical instrumentation like ECG?

So I have spent days reading about specifics of op-amps, instrumentation amps, and ECG circuitry and it just isn't clicking for me. As I understand it, the common mode signal gets amplified and added ...
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1answer
85 views

Bio-impedance circuit inputs

Recently, I wanted to build a replica of a bio-impedance circuit that I found in one of the NIH.gov papers. As obvious, bio-impedance circuits are usually used to measure body composition. They are ...
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1answer
80 views

Failed to build Instrumentation Amplifier

I'm trying to build an instrumentation amplifier, following the schematic attached below. I got two LM358P chips, signal generated by a computer sound card and an oscilloscope. The schematic and ...
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1answer
52 views

Calculating and plotting CMRR

I'm trying to find and plot the CMRR of the following circuit: I'm getting zero for common mode gain, that gives an infinite CMRR for the circuit. When I followed normal feedback laws, I get (2/SRC)+...
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0answers
44 views

Charge injection Compensation for Demodulation

I have a precision application where I am trying to limit the charge injection on an analog mux that is demodulating a sine wave from 0deg and 180deg components (with a trigger signal from a ...
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3answers
57 views

Improved method of instrumentation amplifier input noise and RFI filtering

The following circuit diagrams are taken out of Niel Albaugh's The Instrumentation Amplifier Handbook I understand how the RC (tolerances) mismatches in Figure 4-16 (left circuit) cause the two time ...
3
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3answers
710 views

How to implement gain and offset in a single opamp?

I tried designer here in this page. But my particular case (Case 2) seems not working in the page. Then I Read this document and my case there, is section 4. But my calculation results are not ...
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1answer
65 views

Amplifying Millivolts with a Single Power Supply Op Amp in a Large Gain

I have a signal around 1mV-10mV to be amplified. This signal should be fed into an ADC (ADS1115 ) which has minimum full scale range of 0.256V. So the gain should be at least around 300. I am ...
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1answer
85 views

Instrumentation amplifier protection from high voltage transients with minimal signal degradation

I am looking to protect an INA849 at 2000 or more gain from high voltages of 30 volts AC at various frequencies. Currently I am using an analog switch IC as the only time the high voltages are sent ...
3
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1answer
64 views

Input protection for instrumentation amplifier

There were a few concepts mentioned in the Input Protection Basics from A Designer's Guide to Instrumentation Amplifiers, page 5-5 that I don't quite understand: Why direct transient to power supply ...
2
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1answer
57 views

Respiratory rate monitor

I have this project to build an instrumentation system to measure the respiratory rate. We decided to use a thermistor to measure the variation on the temperature of the air inhaled and exhaled. To ...
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0answers
41 views

Instrument amplifier output continuing drifting

I'm using AD8226 to amplifier differential signal coming out of a load cell, the output of the AD8226 goes straight into the AD7190. My load cell is full bridge with output impedance of 350 Ohm, ...
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4answers
308 views

Output from TD100 with instrumentation amplifier not as expected

I've been having trouble with my TD100 circuit for a few days now and I cannot understand why the output isn't as I expect. This is the process: simulate this circuit – Schematic created using ...
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6answers
114 views

AD623 in-amp output not making sense

I'm planning to use the AD623 in-amp for voltage-difference amplification in a project, but I'm having some issues with getting it to work as wanted. Right now I'm actually just testing the in-amp so ...
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1answer
51 views

Op-Amp Input Common Voltage Range for specific gain

This is the circuit I am working on. I am using this instrumental amplifier AD623 with a gain of 100 using a 1k resistor between pin 1 and 8. (https://www.analog.com/media/en/technical-documentation/...
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1answer
50 views

Differential and common mode over-range indicator for In-amp

I need some advice with differential and common-mode over-range indication. I have a device with In-amp and I would like to add a Led or buzzer for differential and common-mode over-range indication. ...
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1answer
20 views

Instrument amplifier REF pin current

I'm using AD7190 to sample 4ch differential voltage, but the AD7190 only has four input pins. To fix that, I use AD8422 to convert four differential signals to four single-ended signals. The schematic ...
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4answers
744 views

Active guard shielding for instrumentation amplifier

I want to use the the AD8221 amplifier as a conditioner for my load cell. I saw that to reduce noise I can use an "active guard shield driver" between the "REF" of my amplifier and ...
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1answer
93 views

Instrumentation amplifier output attenuation in LTSpice

My task was to design an instrumentation amplifier with given specifications and simulate it on LTSpiceXVII. We were told to only use one type of ac source, so to get the inverted signal I used a ...
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1answer
59 views

Instrumentation Amp design for breaking ground loops between systems

We're in the midst of designing a device for measuring analog signals and have been testing our initial prototype. We had a single-ended gain stage before the ADC, but due to the connections in the ...
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2answers
43 views

Different voltages for Single and Dual-supply (INA)

Since it doesn't matter for the Op. Amp. itself, the components presented as "single-supply" commonly relate to rail-to-rail input/output devices, which operate on lower total voltage ...
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3answers
386 views

What is an instrumentation amplifier and how does the AD524 work?

I am struggling with instrumentation amplifiers. Particularly, I would like to know what defines an instrumentation amplifier what kind of circuit configuration could be classified as an ...
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5answers
277 views

Accurately amplifying a number of current sense transformers

I've got 16 current sense transformers that are being used to monitor AC loads. The SCTs are current output type, producing 50mA on a 100A load. The maximum burden resistance is 10Ω, thus the voltage ...
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1answer
58 views

Feeding a signal directly to an ADC or amplifying (active) it beforehand? [closed]

I am working on a project, where signals have the following characteristics (skip this if you are familiar with EEG): amplitude in 10's or 100's of microvolts frequency range: 1 to 100 Hz Low SNR ...
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2answers
60 views

Amplifying the output voltage from a coil (10Hz-20kHz) using an AD620 module

Disclaimer: I’m computer scientist. I would need some help to get an AD620 amplifier module to work. Some context is available here in a previous question. Here is a physical view of the amplifier: ...
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0answers
33 views

Additional gain with in-amp for nanovolt-scale pre-amp

Currently I'm designing a pre-amp for detecting nanovolt-scale(~100nV, <1kHz) signal for experiment. I need a final gain to be around ~100000. Since the magnitude of the signal is extremely small, ...
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1answer
78 views

Isolating and instrumentation Amplifiers, does the order matter?

I've been reading up on the concepts of properly isolating sensitive signals in applications like analog front ends. For small signals, it is appropriate to use an in-amp. I understand that. But what ...
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0answers
65 views

How can I amplify a square wave signal with a mosfet?

I have a CCD camera that is triggered by an external TTL square wave. That is each time the camera sees a rising edge on the square wave it takes a picture. The square wave is being output from a ...
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0answers
96 views

Differential integrator vs standard

I want to integrate/amplify a very small signal (relatively short pulses of 100ns to 4ms, necessitate high-bandwidth components minimum 40MHz+). The capacitors will be switched (shorted) when not in ...
0
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0answers
25 views

MPX2200DP signal value reversed when amplified with AD620

I am trying to measure differential pressure with MPX2200DP. According to the datasheet, the signal is linear and its value ranges from 0 to 40 mV. To be able to use the sensor properly, AD620 ...
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1answer
278 views

Using LTspice to simulate common-mode signal interference in a differential amplifier?

I'm experimenting with differential amplifiers, and I'm trying to simulate some ways that the common-mode rejection ratio of a DA in the real-world would be decreased. (In other words, ways to ...
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1answer
46 views

Best way to combine different frequency sinusoids to simulate noise?

I'm designing a differential amplifier to remove noise from a signal, and I'm trying to verify my design by simulating a noisy input, but I'm not sure how to do this. The diagram below is roughly what ...
0
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1answer
103 views

Op-Amp / In-Amp (INA826) as voltage divider

We're trying to buffer (for safety, ruggedness and scaling reasons) the input of a µC via some instrumentation-amplifier : INA826 We had our eyes on a schematic in TI INA826 datasheet The only ...
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0answers
38 views

Can I use two AD623 instrumentation amps on one shunt to cover broader current range?

I'm working on building a circuit with an ESP8266 module. I'd like to track its current consumption over time so I've cooked up a scheme to use a microcontroller dev board (Arduino or something ...
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1answer
39 views

Common voltage of 2 op amps instrumentation amplifier

I am trying to build an amplifier for a strain gauge sensor using the 2 op amps instrumentation amplifier design provided in the Texas Instruments note: https://www.ti.com/lit/an/sboa247/sboa247.pdf?...
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2answers
86 views

How closely do the input buffer op-amps need to be matched on discrete instrumentation amplifiers?

For discrete three op-amp instrumentation amplifiers, we know it is very important that the resistors be matched. https://en.wikipedia.org/wiki/Instrumentation_amplifier However, I have found almost ...
3
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1answer
150 views

Trying to increase resolution of ADC using an op-amp

We currently have a circuit measuring a thermistor in a water tank, passing through a couple of voltage dividers and then plugging into an 12bit ADC which eventually interacts with a microcontroller ...
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1answer
35 views

Selecting between 60V source and 1uV measurement

My goal is to perturb a sample with a 250us pulse of 100mA at 60V, then on the same probes measure the response over time in microvolts. The pulses will be repeating at about 100Hz, so most of the ...
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1answer
91 views

Reverse polarity protection on AD623 inputs used to measure low voltages on a sense resistor

This circuit used to measure low voltages on a sense resistor is part of my current meter in arduino that measures currents from 0.005ma to 5A. I configure the gain of the instrumentation amplifier ...
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3answers
186 views

Instrumentation amp vs buffered difference amp

The topology often used within integrated inamp packages often look like this (where the gain is conveniently set by a single resistor): There is another topology that looks more like a buffered ...
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1answer
94 views

Suitable op-amp and voltage regulator for 16-bit ADC

I would like to use the AD4008 16-bit ADC from Analog Devices to sample a load cell. I also need a linear regulator and driver amplifier and instrumentation amplifier. I am curious to know if these ...
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1answer
42 views

How to measure the voltage over a transducer? aka how to measure ultrasound

I want to measure ultrasound. For this task I bought a sensor, and an instrumentation amplifier. Apparently it doesn't work the way I thought because when I test it with a sample 40 kHz wave as input ...

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