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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Improved design for high precision resistance meter

I'm designing a high precision resistance meter, which will measure the change of resistance of a given remote resistor, which is not placed on the circuit PCB, against temperature. The target is to ...
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Which are better and more accurate alternatives to LMV324 by Texas Instruments? [closed]

I need LMV324 form my electronics circuit, but it is not available in India, and someone said there are more accurate quad amplifiers available than this. Can someone tell more quad amplifiers with ...
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Overall CMRR of analog front-end

My analog front end input consists of a chain of (instrumentation amplifier + differential amplifier + and ADC). Is the CMRR of the overall chain only considered based on the first element that is ...
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Which variant of amplifier to use?

I am making a pressure sensor circuit according to page ten of the manual here. There are just too many types of the recommended sensor LMV324 available in the SOIC type. Can someone help me decide ...
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Is it possible to connect a Vin to a ref of an instrumentation amplifier?

I have a circuit in which I need an instrumentation amplifier (INA128 (datasheet)) to be connected correctly for it to work. I don't know if it needs another resistance or if the input needs to be ...
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Need help to understand this circuit

I'm trying to understand this circuit, it's been a long time since I messed with electronics. I even managed to understand some things, for example: The first ICL7660 circuit will be used as a source ...
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2 answers
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Why are there so many variants of an Op Amp? Which one to chose? [closed]

I am directed in a user manual (Page 10) to use the LMV324 Amplifier. But when I search on the net there are just too many types of this amplifier with a lot of different types of suffixes. I need to ...
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Failed to find DC operating point for AC analysis LTspice

I finally successfully added the MCP 606 (MCP 609) in LTspiceXVII. I am now facing an error "Failed to find DC operating point for AC analysis". I have checked the maximum supply of MCP 606 ...
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How do I connect a female EEG electrode to a breadboard?

Electrode output end: EEG electrode: I'm trying to connect the output of EEG electrodes to a breadboard as input. How do I connect the electrode to the breadboard? Usual jumper wires don't seem to ...
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I want to start by doing a circuit analysis of the triferential subtractor

I want to understand the circuit of the triferential subtractor: in the context of Anderson loop based signal conditioning, found in this resource here. This is just an inverting amplifier with a ...
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What would be the amplification circuit for PP02 sensor using LM324 pressure sensor?

I am planning to use the PP02 Omron pressure sensor. The user manual of the sensor (Usermanual link) suggests using LMV324 type of instrumentational amplifier with four op amps within in the schematic ...
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Oscilloscope "isolated" inputs

As I don't want to see my oscilloscope go up in flames when I play with probing circuits, I was wondering the following: First off, my goal is to measure different floating voltages aka the "GND&...
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Options for current sensing for a 230V , 100 W boost PFC circuit?

So I have the following boost PFC circuit: I wish to sense the inductor current. My first thought was using shunt with instrumentation amplifiers, but the issue is total voltage across the inductor ...
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1 answer
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INA128 - what is wrong with this circuit?

I built a circuit based on the INA128 which for some reason heats up rapidly. The test setup is like the image below. The output is left unconnected, no input signal. I get around 550mV voltage drop ...
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2 answers
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Is there an affordable way to balance a bridge without using expensive resistors?

I have a full and balanced bridge circuit with four through-hole \$ 350 \,\Omega \$ resistors and an instrumentation amplifier AD8293G80 that has a gain of 80. Both the bridge and the amplifier are ...
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How to make sensor input look like high impedance on loss of 5V power?

I have a strain gauge sensor with a full-scale output of about 8mV and an output impedance of 5K ohms. We will be measuring its value with a max sample rate of 500Hz, and 10 bits of resolution. It ...
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2 votes
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BMS Two Stage OP Amp

My company is designing a 4 cell BMS. We recently did a redesign of our cell voltage measurement circuits and are having major issues. The first stage of each amplifier is a differential opamp with ...
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2 answers
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Trouble simulating an instrumentation amplifier on KiCad

So... I'm trying to build an EMG sensor for biofeedback purposes, but I'm having loads of trouble both on the breadboard and on the CAD side as well. I'm using a M1-processor mac mini which could be a ...
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Amplifier detector circuit simulation

I wanted to do falstad.com simulation of the circuit(link to schematic): Falstad isn't familiar to me, so I'll be grateful for showing me how it should be drawn. I think detector could be replaced by ...
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1 answer
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Output Voltage of Instrumentation Amplifier Configuration

I'm trying to find the output voltage using the superposition theorem for this circuit configuration when RG is connected. I'm working with ideal op amps. As far as I understand the circuit, when VB ...
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Instrumentation amplifier AD8293G160 - Why RC filter calculations don't match?

I am using an AD8293G160 to handle a signal, for a known bandwidth. The part is an INA with a fixed internal gain of 160x. It has 2 outputs, one direct, the other with an integrated 5k resistor to ...
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Why would I want to use a differential op amp configuration while amplifying differential signals?

A basic instrumentation amplifier looks something like this: My understanding is that you can feed this circuit with a differential signal while not loading the signal too heavily because of the high ...
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1 answer
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Is one RLD electrode enough for multichannel ECG acquisition system?

I am trying to design the multichannel ECG measuring device. My device has to acquire 3 signals at the same time. I have to use 6 electrodes to be able to measure those signals. My problem is each ...
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2 answers
102 views

Why is the output of this instrumentation amplifier not constant?

So here's the circuit and output voltage, the model is AD620: So according to theory (Vout = 49400/49400 +1)*(2-1) ) i should obtain 2V as the output voltage. Well what i got in LTSpice was a value ...
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Does CT act as a constant current source for a specific primary current?

I connected several resistors (1, 10, 100, 560 Ω) at the output of a 1000:1 CT (0-100 A measurement). I saw that the secondary current doesn't change for different resistors for a constant primary ...
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What are the advantages of an instrumentation amplifier over a single op amp amplifier? [closed]

Basically, strain gauges are going to be connected to a Wheatstone bridge and the output from the bridge will be amplified by an instrumentation amplifier. But what are the advantages of this over a ...
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Instrumentation amplifier for high impedance on both inputs, why it is beneficial

Instrumentation amplifier is a differential amplifier with two voltage followers before it. This solves the issue with that an op amp differential amplifier will provide a low impedance path through ...
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4 votes
2 answers
928 views

How does a driven right leg work?

A driven right leg (DRL) circuit is often added to a biopotential amplifier to reduce the common mode voltage (i.e. to increase the common mode rejection ratio, CMRR). A basic form of biopotential ...
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1 answer
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Why does gain of my INA2332 change with increase in input voltage?

I'm building an IoT circuit for sensing resistance change using Kelvin's 4 wire. I have implemented a constant current source that supplies my two sensors connected in series with 50 mA. The output ...
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6 votes
2 answers
739 views

Why is the instrumentation amp distorting the signal on the input?

Here's my schematic. A current source is driving a resistive sensor. The sine wave is to mimic the behavior of the current real supply and doesn't play a role in the distortion. It's approximately ...
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How do you measure the differential gain in an instrumentation amplfier?

How can I measure the differential gain Ad from the formula s = Ad(e1-e2) in the following circuit?
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AD8421 output AC or DC? [closed]

Is the output of the AD8421 AC or DC?
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Current Sense Amplifier / Differential Amplifier Negative Voltage On GND pin OK?

Right now I'm picking a current sense amplifier for my application, and I'm looking for for amplifiers with maximum offset voltage of below 50uV (and offset and bias currents in nA/pA range). Luckily, ...
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1 vote
1 answer
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Why does the input of the op-amp introduce a DC offset to my signal?

I'm interested in measuring the resistance change in a sensor (pk-pk about 1ohm) using an instrumentation amplifier. I chose to go with a constant current source to get the best possible sensitivity ...
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3 votes
1 answer
110 views

Digitally tunable gain, low-noise instrumentation amplifier

I want to make a digitally-tunable gain (~1 to 1000x), low-noise instrumentation amplifier. There are integrated ones (e.g. AD8557) but the input noise is too high. My current plan is to use an ultra-...
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High voltage current sensing with floating isolation amplifier

I need to sense 200V (to GND) 0.5mA - 20mA DC with minimum components count. After a lot of searching I think isolation amplifier followed by post-amp would give least components count. Isolation amp ...
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2 answers
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PIR sensor amplifier with minimum component count

I'm new to opamps and I could use some help amplifying a PIR sensor and output to a microcontroller. Minimum component count without compromising performance (highly integrated solutions). Here is a ...
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1 vote
2 answers
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How to make this arbitrary waveform?

Im trying to generate a custom waveform based on the instrumentation amplifier. The concept is that using two signals* , square 2Vpp and triangular 1Vp, get the next output: Under the next ...
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Negative voltage value for AD620 amplifier

I am using AD620 to amplify the signal of a pressure sensor, and a negative supply voltage must be added to V- pin. should the negative voltage value be the same as the positive supply voltage? or any ...
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2 answers
341 views

How does an Instrumentation Amplifier reduce DC offset?

While researching different current measurement methods, I came across a particularly interesting circuit which has a very high input impedance and apparently reduces the effects of the input offset ...
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1 in 2 out portable headphone amplifier

Here's my idea of a portable headphone amplifier. A line receiver INA1650 (instrumentation amplifier with all its benefits) that feed two LM4880 that drive the headphones (with separate volume control....
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5 votes
2 answers
1k views

Instrumentation Amplifier with a gain of 1 doesn't output a different signal

I just bought an instrumentation amplifier, INA828, and not sure why but it is not outputting what I want. I was hoping that it would simply be a differential with the buffer included but it seems ...
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8 votes
6 answers
2k views

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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3 votes
1 answer
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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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2 answers
51 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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1 answer
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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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1 answer
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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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3 answers
114 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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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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1 answer
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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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