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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Level-Shifting not working in Instrumentation Amplifier

I want to shift the measured EMG input signal to the positive side to use ADC. I used the REF input of AD8421 to add an offset of 2.5V. I simulated the circuit below from the AD8421 datasheet on ...
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Does the ADS1115 need an instrumentation amplifier? [closed]

I want to use a ADS1115 to digit analog output of a sensor. The sensor gives 2mA, so I have to use a amplifier. I want to use a instrumentation amplifier, the LTC2053. But I just read the datasheet of ...
DamanZ4's user avatar
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Unexpected signal at AD620 module output when Vsupply is on

I bought an AD620 instrumentation amplifier module and below is the module schematic. Souurce - https://protosupplies.com/product/ad620-instrumentation-amplifier-module/ A problem shows up when I'm ...
Jack Huang's user avatar
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1 answer
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Recommendation for type of switch [closed]

What type of switch would you recommend for the diagram below?
fluggy 55's user avatar
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Input impedance of instrumentation amplifier

I have a problem understanding which resistors set input impedance of an instrumentation amplifier. What is the input impedance of the circuit given and what is the purpose of R250 (10k to GND)?
cubix's user avatar
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Choosing a supply voltage for an instrumentation amplifier

I am using a Wheatstone bridge to measure a resistance and an instrumentation amplifier to amplify the signal. Specifically, I am using the INA121. According to the amplifier datasheet, the input ...
user386164's user avatar
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Instrumentation amplifier using folded cascode op-amp is not working

I made the sizing for a folded cascode operational amplifier, which is working well, however when I am trying to implement an instrumentation amplifier in LTspice using the blocks, it does not amplify ...
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Do we have to share the ground between a load and a sense-resistor based current meter?

I see in the datasheets of some current-meter chips, that the LOAD ground is also the same as current-meter chip (inAMP for example) ground. For example AD8293 inAMP: Or this model (INA3221) from ti: ...
Tirdad Sadri Nejad's user avatar
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LT1970 output changes when I probe the voltage

I'm using an LT1970 for current control. I read the current with a shunt resistor and an AD8421. When I connected the circuit to a 10 Ω load, the AD8421 read 134 mA, but when I tried to measure the ...
SASKEEEEH's user avatar
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3 answers
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INA828 monitoring current shunt charging and discharging question

I am designing a battery current shunt monitor that measures current while discharging and also charging. I am planning on using the INA828 amplifier feeding an ADC. My questions revolve around the ...
Barry Jensen's user avatar
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Instrumentation Amplifier improper frequency response

Followup to this question. I have an instrumentation amplifier. When conducting an AC Sweep, this is the response. There are two issues with this. Firstly, the signal magnitude is far too low. ...
HFOrangefish's user avatar
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Common mode voltage with configurations of Opamp

I am reading this article (https://www.analog.com/media/en/training-seminars/design-handbooks/designers-guide-instrument-amps-complete.pdf) in order to understand more how traditional instrumentation ...
TSLee's user avatar
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Input common-mode range vs output voltage (INA826) interpretation

I'm starting a new design using INA826 and analyzing the input common mode limitation, I do not understand the differences between this curves; I mean, why in figures 11 and 12, gain and VS is not ...
Facundo Piñero's user avatar
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1 answer
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INA114 vs INA826: why is the INA114 so expensive?

I have been using the INA114 in my design, but wondering if I can use the INA826 instead. I cannot figure out what the difference between these two instrumentation amplifiers is. The CMRR is nearly ...
Dillon Stewart's user avatar
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Are these switches really necessary?

I'm analyzing the OpenBCI Ganglion board and I reasoned that switches SW1 through SW4 (part number CJS1200) might in fact be useless. The negative input for each channel (X_IN-) is connected via a ...
AlexanderCar's user avatar
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No output when testing the AD620 amplifier with a function generator

I have a problem testing the AD620 amplifier using a function generator. I'm injecting a 100 mV sinusoid, and with the gain of a 1k resistor. In this configuration I would have a 5 V signal at the ...
Lilian Pereira's user avatar
2 votes
5 answers
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Asking advice for designing an analog circuit with amplifiers

This is my first time trying to create a circuit by myself. I have been learning different combinations of circuits such as a differential amplifier, some kind of basic circuits with an operational ...
TSLee's user avatar
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INA128: EMG signal output voltage shift when leg touch the ground

I followed this circuit to get the EMG signals (dual supply +-9 V). I set the Rg at 330 Ω (at 2.8 kΩ, I can't see any changes in the output, so i set the gain higher), and replaced OPA2131 with TL072 ...
MonhVuv Vu's user avatar
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2 answers
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Advice on Designing a Low-Current Photodiode to Digital Pulse Circuit

I'm currently working on a project that involves converting very low photo diode current pulses, typically around 100nA, into digital pulses. The pulse-repetition frequency (PRF) is about 10 kHz, with ...
kakeh's user avatar
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Non-constant active filter gain

I designed an amplifier using an instrumentation amplifier and an operational amplifier. Here, I used a 2 Hz high pass and 100 Hz multi feedback low pass filter, but I could not get the efficiency I ...
atıf koçak's user avatar
1 vote
1 answer
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ad8426 instrumental amplifier design

I'm having a problem with my AD8426 instrumental amplifier design. As I show in the image, I use a 3.3 V supply and after increasing my input signal, I use 1.8V virtual ground to make it oscillate on ...
atıf koçak's user avatar
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How to interpret input common-mode voltage vs output voltage in INA823 Datasheet

First, a similar question was asked before Understanding common mode vs output voltage graph for instrumentation amps, however, I failed to understand it with regards to my use case and need more ...
tronhawk's user avatar
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Challenges in measuring the output voltage of an H-bridge using an instrumentation amp and resistive divider

Design a circuit that allows me to measure the output voltage of a full H-bridge. Essentially, I'm using a resistive divider for this purpose. The simplified design is as follows: I had issues with ...
WalterPH's user avatar
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50 Hz noise on INA125 for Wheatstone bridge application

I am trying to measure mechanical deformations using a full Wheatstone Bridge. In order to do that, I connected the bridge to an instrumental amplifier (INA125PA). The amplifier is powered with a dual ...
Benjamin SCHMIDT's user avatar
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120 views

Output voltage thermocouple amplifier decrease when temperature increase

To detect surface temperature of heating foil, I decided to use thermocouple of type K. To amplify the small signal I choose the thermocouple amplifier with cold junction compensation integrated, ...
stefyanna's user avatar
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4 answers
633 views

Wheatstone Bridge with Instrumentation Amplifier

I have set up this circuit: I measure an output of 0.61 V from the instrumentation amplifier. The gain of the amplifier is set to 21. The formula for the output is given by: Uout=(1+2R1/Rg)×(R3/R2)×(...
Eirik's user avatar
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Multiple 4-20mA Transmitters from Common Referenced Analogue Inputs

I'm trying to come up with a scheme for multiple loop powered 4-20mA transmitters controlled from seperate analogue voltages, which all have a common 0V reference. My inital thought was to use an ...
Dan Twining's user avatar
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The output of my instrumentation amplifier (INA121) is not seen in the microcontroller (MSP430)

I am using an INA121 instrumentation amplifier, and its output is 156 mV, but it is not seen in the microcontroller, it is just giving 0 like: I increased its output voltage (gain) by decreasing the ...
Merve Özdaş's user avatar
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1 answer
153 views

INA333 strange output, it's the same w/ and w/o input

This is the EOG (Electroencephalography circuit I'm working with) The output is essentially noise when I hook up the electrodes to myself, hence I'm debugging each stage, hooking up to an ...
roaibrain's user avatar
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12 lead ECG electrode configuration in circuit

I have one little misunderstanding about this diagram, how are the 9 ECG electrodes attached to INAs input legs, as there are even number of them (respectively 10)? Additionally, I'm not sure where ...
Nika Abashidze's user avatar
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Voltage reference vs voltage bias for EOG circuit

This is continuation of my previous question. I'm confused about the reference voltage and bias voltage. As seen in the image above, the supplies for the INA333 and OPA2335 are clearly 3.3V and ground....
roaibrain's user avatar
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Why does this instrumentation amplifier (INA110KUG) output 9.8 volts even when input voltage is 0V? What am I doing wrong?

I've tried removing the resistors from the upper side but there was no change in output voltage. Datasheet:https://www.ti.com/lit/ds/symlink/ina110.pdf
Andrei Grigore's user avatar
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1 answer
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Instrumental amplifier outputs in 12 lead ECG [closed]

Currently we are trying to build 12 lead ECG circuit, so we just need to know the answers to couple of questions. Why do instrumental amplifiers on given circuit have two outputs? How are they ...
Nika Abashidze's user avatar
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1 answer
58 views

How to design gain based on input voltage and ADC voltage range?

What are the parameters to consider when designing gain amplification whether it be 2- or 1-stage (why one or the other?) when given an input and an ADC? I see for the same kind of signal (biosignal) ...
roaibrain's user avatar
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2 answers
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Why is does my INA121 instrumentation amplifier not amplify my load cell's signal at high loads?

I am applying a high load (150-200lbf) to a (mV Wheatstone bridge) load cell rated for 200lbf (link to datasheets at bottom), and amplifying the differential signal with the INA121 instrumentation ...
Eric's user avatar
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1 vote
2 answers
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How to understand the noise specifications of amplifier?

LT6370 Instrumentation amplifier has specifications as below. How should I understand this specification? Why only 0.1 to 10 Hz is specified, why not high frequency values? Thanks in advance.
E2.0's user avatar
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1 answer
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Problem about Instrument amplifier from LM358 at high frequency

I am researching about instrument amplifier circuit by use op-amp is LM358. In this circuit gain is 1 by Rgain=R2=20k, R1=R3=10k. Testing is define frequency range 1 Hz-10 kHz but when this circuit ...
EricSphere's user avatar
-1 votes
1 answer
62 views

Baseband circuit is not working as expected

simulate this circuit – Schematic created using CircuitLab The circuit when printed on PCB, output isn't a bandpass signal as expected. When I am checking the output with CRO across output pin ...
Sreya Ghosh's user avatar
3 votes
1 answer
61 views

Help with understanding why my instr. amplifier doesn't return anything

I have a pressure sensor (output -> Wheatstone bridge) connected to an amplification stage, as shown here: As you can see, four points in total are attached to the ADC of my MCU (STM32L476ZGT3.) ...
mdir's user avatar
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AD620 or INA114 for EEG Device

I am trying to design an EEG device and found these suitable low cost instrumental amplifiers. I read their datasheets but could not find any significant differences. Which one is generally better? I ...
Tombeki's user avatar
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1 answer
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How to determine the limiting current resistor for instrumentation amplifier

I am using this instrumentation amplifier to measure the output voltage from a solar cell. This IC has the input protection by using a resistor Rlim, and the datasheet includes the equation for ...
Alex's user avatar
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0 answers
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Logarithmic Amplifier

Which part of the circuit acts as a constant current source in logarithmic amplifier using transistors ?
Rajesh Raskoti's user avatar
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1 answer
127 views

Function generator cannot generate differential voltage?

I am using the AD620 as instrumentation amplifier to amplify the body's ECG signal. An ECG is a differential signal (measured with two electrodes) and I want a differential gain of \$G_d = 1000\$. The ...
Carl's user avatar
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RTD - convert measured voltage to temperature

I have a 3-wire RTD connected to a Wheatstone bridge and then to a INA. The Vout from the INA is then connected to a ADC. How can I convert the measured voltage from the ADC to the respective ...
UKNP's user avatar
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2 answers
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First-order filter between sensor and amplifier

I need to sample an analog pressure sensor (TSCDRRN015PDUCV) with very high accuracy. The pressure sensor is currently connected to an instrumentation amplifier (AD623) and then sampled by my MCU's ...
mdir's user avatar
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2 votes
2 answers
397 views

Amplifying mic signal with instrumentation amplifier

I'm trying to amplify my dynamic microphone's (SM57, 1.6 mV OCV, 150 Ω) differential signal to about instrument pickup level (-20 dB) to drive effect pedals. Currently, I'm testing with an AD620AN to ...
Andrew Li's user avatar
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2 votes
3 answers
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Common-mode gain of an instrumentation amplifier buffer stage

We discussed an instrumentation amplifier: We were given the common-mode gain of the buffer pair (Op1 and Op2) for the common-mode output voltage \$\frac{1}{2}(U_{a+}+ U_{a-})\$ to be \$1+\frac{\...
Ondry's user avatar
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5 votes
2 answers
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Coupling floating differential inputs to an amplifier with/without resistor pair

My question is about wiring a "floating differential input" signal to an instrumentation amplifier. I've read that in the case of a floating signal two high value resistors are used to ...
ty_1917's user avatar
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How do I get a 1.5 V reference voltage from a 3 V coin cell battery? [duplicate]

My goal is to build an amplification circuit powered by a 3 V coin cell battery that uses an instrumentation amplifier to read a differential voltage. The instrumentation amplifier chip has a ...
dinoswords's user avatar
4 votes
2 answers
408 views

Differential to single-ended converter (ARINC 429)

I'm trying to design a circuit to take a ARINC 429 signal and convert it into a signal that can be read by a microcontroller. This will not be airborne and is just to interface a real radio with a ...
George Gohl's user avatar

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