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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1answer
48 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 ...
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1answer
53 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
289 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
100 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
40 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
34 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
19 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
515 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
65 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
47 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
33 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
351 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
232 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
54 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
48 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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23 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
44 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
54 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
51 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 ...
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18 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
128 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
43 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 ...
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1answer
74 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
37 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
38 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
69 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 ...
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1answer
122 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
79 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
176 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
77 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
38 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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2answers
272 views

How to calculate the current / power consumption of instrumentation amp with op amp as an impedance converter at REF input

I have a measuring bridge and want to connect it to an ADC with an AD8227 instrumentation amplifier (Datasheet). For the reference voltage, I have connected a voltage divider to an LP358 as an ...
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2answers
115 views

AD623-Unable to change gain or reference voltage

I have an air flow sensor (FS1012-1100NG) with expected differential output voltages ranging from -1mV to 20mV and I need to 1) know the precise value (mV) and gain to correlate V with airflow 2) make ...
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1answer
61 views

Instrumentation amplifier & microcontroller ADC protection circuit

I have a couple questions related to protecting my instrumentation amplifier and the ADC of my MCU. The circuit is as shown in the image, with the input to the in-amp (an AD8223) being a very weak ...
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1answer
48 views

Instrumentation Amplifier Gain set resistors

We are looking for Instrumentation Amplifiers for an application.  At this stage, we have decided a certain gain value for our Instrumentation Amplifier. The datasheet of the product mentions the very ...
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2answers
56 views

DC offset before signal being fed into an instrumentation amplifier from a bio potential source

I am trying to design an instrumentation amplifier, having 2 bio-potential sources as its differential inputs, each having peaks in the order of 10's of uV and a frequency band of 3-50 Hz. One of the ...
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0answers
106 views

One milliamp current source for RTD

I am trying to design a one milliamp current source (Howland current source) with a precision of +/- 1 uAmp. The current source will be used to measure temperature with a 3 wires RTD sensor (H-T-01-12-...
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3answers
152 views

Instrumentation amplifier didn't fix my ADC crosstalk, and I don't understand why

A previous iteration of my circuit was as follows: I am sensing DC voltages across 6 variable resistors (1kΩ Pt RTDs) The 6 resistors are connected in series; the series is connected to a current ...
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0answers
28 views

What is the best TVS/ESD protection for Wheatstone bridge circuit?

I have 150K ohm on three legs of Wheatstone bridge, one leg on human body (skin), bridge excitation voltage is 5V, differential amplifier is be used to read the differential voltage of the Wheatstone ...
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1answer
157 views

What does Vaa mean?

I'm trying to understand this circuit. It looks like all the NCP chips are just voltage regulators, but I don't understand the VDD and VAA labeling, what do these mean. Also, any idea why the top ...
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1answer
38 views

Is it possible to replace the ref pin of AD620A with a fixed voltage?

I am trying to implement the below circuit (from) without ADuC842, I will use Arduino mega2560 ADC. the circuit generates -5V to 5V rail to rail voltages for ad620a and they control ref voltage via ...
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0answers
20 views

Switched-cap/charge pump only way to generate negative rail voltage for op-amp?

I need to design a daughterboard that gets mounted directly to a piezo mic to condition the signal before transmission. Part of the conditioning is a full wave rectification. Thus, as you'd expect ...
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2answers
105 views

Amplification Circuit for Generating High-Current Sinusoidal Signal to Feed a Coil

I am trying to implement a control algorithm using Arduino Due. I need to generate high-current constant-frequency sinusoidal signals to feed a coil using some batteries. The coil will generate ...
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1answer
76 views

Resistors in an instrumentation amplifier

I'm designing a circuit where I'm using instrumentation amplifier to amplify my input voltage The formula for the amplifier is $$\frac{V_{\text{out}}}{V_{\text{in}}} = \left(1 + 2\frac{R_1}{R_{\text{...
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2answers
983 views

What does m% stand for?

What does m% mean? Like in this datasheet from TI at the gain error graphs: http://www.ti.com/lit/ds/symlink/ina149-ep.pdf?&ts=1589388038122 Is it supposed to mean per-cent-mille (10^-5) or per-...
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1answer
32 views

Bias Input Current Compensation for Instrumentation Amplifier

What is the motivation to choose R1=R5=5k6 Ohm? If they are for bias current compensation and both OP Amps have same Bias input current, 10k should be taken in my opinion to eliminate common mode ...
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1answer
40 views

Instrumentation amplifier dealing with wire resistances

Can anyone please help me in understanding the output of this amplifier? According to me it is coming as (E1-E2)(1+(Rw/R)). I am more curious about knowing wheather Rw will come in the output ...
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29 views

Evaluation of multiple Wheatstone bridges using one instrumentation amplifier

I need to measure 8 different strain gauges. I am thinking about using just one instrumentation amplifier to evaluate all Wheatstone bridges (because of the high price of instrumentation amplifiers.) ...

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