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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34 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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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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40 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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52 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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How to test an ISO100 optically coupled linear isolation amplifier

I have these components and have to test whether it is functioning properly by building a test circuit. Not able to come up with an idea can anyone suggest please and provide some details about it. ...
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37 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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16 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
49 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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42 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
54 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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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
34 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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63 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
104 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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33 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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66 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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102 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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67 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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37 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
159 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
84 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
39 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
45 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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49 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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89 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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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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24 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
91 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
32 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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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
93 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
53 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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974 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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27 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
39 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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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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1answer
63 views

Measuring current, instrumentation or differential amplifier?

I want to measure current at the high side of circuit with 0.1 mV accuracy using a 16 bit ADC. for sensing the voltage drop over a 100 mΩ 1% resistor I need to use an op amp which is cheap and easy to ...
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4k views

mV variations even with a simple voltage divider

edit: After using a prototype pcb instead of breadboard, placing all possible electromagnetic sources away and unplugging all the equipment from the same line, my noise dropped 2 orders of magnitude. ...
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1answer
41 views

Unable to get instrumentation amplifier to work correctly

I have built an instrumentation amplifier using an LM348N quad op amp, supplied with ±9V. A simulation of the circuit is done as in the link - Simulation: But when I connect the circuit accordingly, ...
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528 views

Is AD7794 a good alternative to Hx711 for multi-channel ADC?

note: Electronics isn't my main background so I might make silly mistakes. I did read the datasheet but don't understand all the terms despite my effort. Suggestions are welcome. AD7794 (datasheet) ...
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1answer
80 views

Instrumentation amplifier - schematic review

I'm trying to make an instrumentation amplifier to measure a sine wave signal of 0 - 1Vpp (max) 50Hz that comes from a non-invasive current sensor (30A SCT-013-030). It gives 1Vpp at 30A current. ...
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26 views

How can I add an offset voltage at the input of an instrumentation amp?

I want to measure the voltage of an H-Bridge Sensor. However, due to the manufacturing process, the bridge has an offset several times larger than the useful signal (it can easily measured by ...
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1answer
75 views

Advice on generating a negative supply rail (-5V) in an embedded, mixed signal design

I'm designing a board that can take an input DC supply of between +8 and +36V DC (+12V nominally) and needs rails of +5V, +3.3V, +2.5V and +1.8V. My current design uses a step-down regulator (LMR23625)...
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1answer
127 views

Instrumentation amplifier, discrete or integrated?

Since integrated instrumentation amplifiers are so readily available, does it still make sense to incorporate an instrumentation amp discretely built from multiple opamps and resistors? Would one see ...
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89 views

Why use difference amplifiers over instrumentation amplifiers?

I know that instrumentation amplifiers are difference amplifiers with buffered inputs, and I understand why one would select an instrumentation amplifier over a difference amplifier circuit. But is ...
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1answer
96 views

Differential RC filter

I sometimes see differential filters like this: And sometimes this : Basically sometimes there are 3 caps (2 going to ground on each input), sometimes I only see 1 cap ( 1 differential cap, none ...
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62 views

Use a precision opamps or instrumentation amplifier for load cell application

I'm making a low power weighing scale with good precision. I'm contemplating if it'll be better to build a instrumentation amplifier with discrete OPAMPs of LPV821 which is low power (Iq 650 nA), high ...
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21 views

Error Propagation and Analysis on a experiment due to Voltmeter Constraints

I got a situation: at the moment I am unable to access both channels for Keithley 2182A nanovoltmeter using LabVIEW. However, for some odd reason, while I cannot access the channels at once, LabVIEW ...
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42 views

How to handle disconnected resistive sensor?

I'm trying to connect a PT100 thermo probe to an Arduino project to measure water temperature. After some research I have found and adopted a design using a Wheatstone bridge and an instrumentation ...
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2answers
83 views

Instrumentattion amplifier gain appears to change

I made a very simple circuit to amplify a ~1 mV signal up to ~2 V. The input is a 0~2 mV DC signal from a scientific instrument. The problem: I made the circuit, and it worked as intended. The 1 ...

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