I have a project that requires an INA134, THAT1240, etc. Those chips are conventional line receivers. Any of them would be expensive to import into my country due to shipping costs.
Here I can cheaply find: AD620, INA114, INA128.
My question is if I can use any of the mentioned instrumental amplifier chips as a (obviously lower performance) replacement and if one them could give me better performance than a design with discrete op amps.
Thanks!
Hi.
I' m going to make a better PCB based on OpenEEG project:
http://openeeg.sourceforge.net/doc/
Better - I mean using SMT components, smaller in size, but with same functions. I worked with EEG before, but not with amplifiers. Anyway, I need to replace INA114 with some instrumentation amplifier in SO-8. I found INA819, INA828 and INA188 at local supplier's. All these amplifiers differ from INA114, some have better CMRR, others have better offset voltage, but neither has both parameters better.
The question is: which one to take, and also, which is more important for EEG - low offset voltage or better CMR?
Looking to build one but have no idea what kind of Instrumentation amplifier to use.
Hey, I'm planning a project in which I'm going to turn a dumb hotplate with only one of those bimetallic thermostat knobs as control, into a smart hotplate with a thermocouple, PI/PID control, a little display, triac switching, the works. Thing is, in research, I've come across how thermocouples need an instrumentation amplifier to amplify their mV signal while also rejecting common-mode noise, which I get and all, but a lot of articles and superficial google searches suggest pre-made Integrated instrumentation amplifiers like the AD621, AD8221, or some little module with potentiometers. I can see the value in using integrated IAs like these with predictable behavior, but would it be, i dont know, "okay" to just make one out of say lm358s and/or a 741 op amp instead, and 1% film resistors? Those with experience on the topic, let me know. My gut says that while I'll save a few bucks, I may be risking precision and other stuff. Thanks.
Under what circumstances would you prefer to choose one over the other?
I am working on an RF receiver, and after my initial mixer / down-conversion I need something like 90dB of gain. There are several stages, with phase shifts, combining I and Q, and some audio baseband filtering, etc.
I was looking at the INA2332 (datasheet here), which lists on page 3 a "gain range" from 5 to 1000. Is there any downside to just configuring it for maximum gain?
Lots of other schematics I look at seem to spread the gain out, and stay way under what seem like achievable levels of gain in any one part. But it's kind of attractive to think I could get the first 60dB out of one device...
What should I be thinking about when I see that "gain range" row in the datasheet?
Thanks!
Greetings, I wanted to simply check my work with you guys who may be more well versed with instrumental amplifier.
I am working with the AD620, which has a gain equation of G = (49.4kohms/Rg) + 1, cool all fine and dandy. Lets say I have a wheatstone bridge, with diagonal resistors, 2 10k and the other opposite diagonals 9k and 11k. Lets say I have a 5v DC power source running through it to get the differential input signals which run to the AD620 of 2.37 >> (5*(9/19)) and 2.38 >> (5*(10/21))...
Now, there is a resistor of 1k between both signals and the AD620 V+ and V- which is apart of a low pass filter with a 1nF caps on both sides, with another 64nF cap connecting the two lines in the middle.
I ran this through I circuit to try and see what the voltages on the positive and neg input terminals of the AD620 would be and I get 771.7uV for one (inverting terminal) and -7.56mV for the other (non-inverting terminal)? I do not understand at all how this is happening??
EDIT: Mistake on simulation, forgot ground on Wheatstone bridge, fixed voltages back to the halved values of the DC input. Vdiff = 12.53mV.
Figure 42 of this datasheet https://www.analog.com/media/en/technical-documentation/data-sheets/AD620.pdf is damn near the exact circuit if you assume that the input voltages are basically the same coming from a Wheatstone bridge.
Hello I am trying to find the CMRR for a three op amp Instrumentation Amplifier. I have managed to find the differential gain for it. Can someone please show me how to find common mode gain or an alternative method to find CMRR for the amplifier
So I am working on an audio mixer using op amps. I am a bit confused on bal/unbal inputs. How can I use one TRS input jack for either a balanced or unbalanced input on each channel?
Sorry if this doesn’t make much sense. I have some balanced equipment and some unbalanced. I would like to be able to plug either into the input jack and not have to worry about putting something in the wrong jack.
If anyone has a circuit that does what I’m suggesting I would really appreciate if you let me know. Also if I am dumb and this doesn’t require anything special, please let me know that too...
"Explain the operation of a transducer bridge circuit using instrumentation amplifier to measure the temperature from 30°C to 70°C and represent output from 0V to 5V. Assume step size as 4 ohms/degree"
I tried assuming a value of R0, then balancing the Wheatstone bridge at 30°C. But how do I bring in the step size into this? I'm really lost rn.
I DMed my teacher and she seen-zoned me on it, so I'm at my wit's end.
Thank you for your time!
I’ve been trying to wire the instrument amp with a potentiometer in place of Rg and also just placing resistors but it’s not working. Regardless of Rg it’s supplying the same gain.
Helpppp
I am having trouble simulating a 3 op-amp instrumentation amplifier in LTspice.
The op-amps I have chosen for the simulation are AD8031 (built into LTspice). The differential voltage is 0.5V, and the gain is about 1.9, so the output voltage should be 0.95V.
However, VOUT is showing 9mV.
https://preview.redd.it/58frs4cipql41.png?width=1496&format=png&auto=webp&s=7d46a4e9fb502a5f5f92f7b4c84d98a37444fde3
Can someone see what I am missing?
EDIT: Thankyou Allan-H - the input voltages were the wrong way around.
Hello! I'm trying to build a pressure sensor with a piezoelectric and an instrumentation amplifier. However, I am having troubles with the instrumentation amplifier since there are a lot of circuit diagrams and the ones I have built are not giving me the results I want. I only need it to give different voltage levels according to the pressure that is being applied to the piezo. (The more pressure you apply on the piezo, the higher voltage it gives). Also, I'm using TL084 operational amplifiers. Please let me know if you have any diagram I could use. By the way, thank you for reading. I'll be glad to read all your sugerences.
I'm trying to implement a driven right leg circuit for a pet project I'm working on. This involves taking the common mode voltage from a differential input, inverting it and sending it back to the source to try and cancel some interference in biopotential recordings.
The issue is that most circuits I'm finding online are clearly taking the low-impedance output from the two voltage followers in a 3-amp in-amp, and using a voltage divider for the common mode (like in this image).
That would be fine if I was making my own 3-amp in-amp, but I'd prefer to use precision matched ICs for the increased CMRR. I considered using a voltage divider at the input, but that would suffer from impedance matching issues, and could affect the inverted common-mode signal for the driven right leg amp. Thanks!
I just love how to see the world through sensors. I have been using modules with sensor amplifiers (probably, in-amps) with my Arduino/ATMEGA328P-PU projects but I want to take it to the next level by designing my own instrumentation amplifiers.
I have knowledge in basic electronics and circuit analysis. I have used some LM358 Op-Amps before as simple amplifiers. Somehow, whenever I read schematics and tutorials about in-amps, I am stumped by certain terms like high-impedance, CMRR, virtual grounds. With this, I guess that I lack some foundation knowledge to begin with.
Can you suggest a learning path towards mastery of designing/using instrumentation amplifiers?
When I try simulating instrumentation in LTspice , i get very large output offset voltages that dont seem to match the datasheet (should be 100-300 uV, not 80mV).
here is an example: https://imgur.com/a/jSc25af
Ive simulated other models as well such as LT1167 and i get similar results.
What am i doing wrong?
https://i.stack.imgur.com/BJGey.jpg
One output pin of a thermocouple is hard-wired to protective earth. Does it still make sense to use an instrumentation amplifier, or can I use a single (low input bias current) op-amp?
From what I learnt, an in-amp is used for thermocouples because of great common mode noise rejection. But when one end is grounded, isn't it defined as 0V and noise-less all the time? Then we'd have a potentially noisy signal on the other end vs. 0V and equal conditions as in a single op-amp ... or am I missing something?
I've got 2 photodiodes with bandpass filters on, for 887nm and 967nm, I'm planning on measuring peaks at both those wavelengths using instrumentation amplifiers.
Since I want minimum noise, I'm thinking I probably shouldn't use the photoconductive mode, which leaves the photovoltaic mode.
I've been looking at:
https://www.hamamatsu.com/resources/pdf/ssd/e02_handbook_si_photodiode.pdf
At Figure 1-18 (a). I was wondering if that diagram is depicting a photodiode in photovoltaic mode attached to an op-amp, but can't tell for sure? If so, could I simply place the photodiode across the inputs of an instrumentation amplifier?
The following is the datasheet for the photodiodes I am using:
https://docs.wixstatic.com/ugd/f74914_d8b36aed8c8a445da4ced66032df3393.pdf
Here's the deal:
- I'm looking to take current measurements at about 10Hz.
- About 75VDC max, ~80A max
- I've tried using Hall sensors, but they seem to be pretty unavailable outside of AliExpress, and then it seems like half of them are wildly inaccurate or DOA. I need something more reliable that I can scale up into an automated testing environment.
- Given the high-power situation, I've decided that a current shunt resistor is probably my best option (unless anyone has any other brilliant ideas). That means I need an instrumentation amplifier.
- I'm planning on using a LabJack DAQ, acquiring data using Python.
- Here's my question: do I just buy a bunch of instrumentation amplifiers, set the gain using a resistor, and then sample away? Is there some kind of combination board or ADC that I should know about that would serve as the amp and the ADC that would have an I2C interface?
Thanks for any advice. I'm just getting into this, and am likely missing some major considerations.
I need to build a instrumentation amplifier to amplify a 100g load cell for a lab. The load cell operates at 3-10V and has a rated output of 600uV/V. I'm planning on using 3 UA741 op amps in this configuration.
Since the load cell operates at 3-10V I was thinking about applying +5V and -5V to the load cell and the op amps.
Under full load, I'm expecting the amplifier to produce 600uV/V * 10V = 6mV. So I'm thinking a gain of ~1500 will give me a range from 0 to 9V on my output.
From the formula given Av = (1+2R/Rgain), I've chosen R = 470kOhms and Rgain = 510.
The output voltage is going to be sent to a 32bit analog input.
Is there anything blatantly wrong with this circuit or my calculations? I'm a total noob and any advice is really appreciated.
I'm working towards my design final and I want to amplify the output of a load cell from 6uv/V @ 10V to a range between 0 and 10V, meaning I need a gain around 1500, while keeping +/-1g precision.
Previously I made an instrumentation amplifier from 3 UA741 op amps. It was a complete mess, and barely worked. So I've been researching and it seems that a microphone pre-amplifier would work well in this scenario.
I've found the INA 166, which seems like it's a good choice. But, it's a little expensive at $13 each. I only need one, but I'd like to be able to purchase a few spares in case I mess something up soldering.
Are there any cheaper recommendations for a load cell amplifier?
Also, I can't use a shield board, I have no way to read the serial output.
Does the following link also apply to Instrumentation Amplifiers in terms of ideal vs real characteristics?
http://www.learningaboutelectronics.com/Articles/What-are-the-characteristics-of-an-ideal-op-amp
I'm trying to make an instrumentation amplifier with a 10v/v gain. My friend asked me for help, and I'm a little embarrassed to say that I couldn't help her out, but her question piqued my curiosity.
From what I knew, gain was decided by the following equation:
(Vout)/(V2-V1)=(1+(2*R1/Rgain))(R3/R2)
But every time she tested it, she got some strange result. Am I wrong about 10v/v meaning that Vout=10(V2-V1)? Any help would be appreciated.
[Here's] (https://scontent.fsnc1-1.fna.fbcdn.net/hphotos-xaf1/v/t35.0-12/12255475_10206247217634307_1308419154_o.jpg?oh=66889b405583527225b6d03f2766e649&oe=5650A7C5) a link to what we're working with.
we are developing instrumentation amplifier using IN128 IC. when we provide same voltage or zero voltage to both the input pins(V1 and V2) the output should be zero but we are getting 1-1.5V how to reduce/remove this offset voltage?
Why do I get a square wave from the output of this in amp (measuring EMG). It's an AD627 and this is my first attempt at analog electronics. There are so many parameters in the datasheet. If someone would point me in the right direction it would be helpful. Apologies in advance for the creepy video. Also, my setup is quite dodgy (i.e using passives, & coins for electrodes, but I don't think I should be getting a square wave).
http://www.youtube.com/watch?v=e2vFFCQq4KE
Schematic: http://i.imgur.com/iGjx5.png (measuring Rl)
Also, the frequency of the output is exactly 50 hz. Mains hum??
I've built a couple of amplifier topologies to meet specs given in electronics classes, but now I'm exploring on my own and I was wondering if there are hidden tricks (biasing, op-amp choice, resistor matching, etc.) that lead to good performance.
Hello I am trying to find the CMRR for a three op amp Instrumentation Amplifier. I have managed to find the differential gain for it. Can someone please show me how to find common mode gain or an alternative method to find CMRR for the amplifier
I just love how to see the world through sensors. I have been using modules with sensor amplifiers (probably, in-amps) with my Arduino/ATMEGA328P-PU projects but I want to take it to the next level by designing my own instrumentation amplifiers.
I have knowledge in basic electronics and circuit analysis. I have used some LM358 Op-Amps before as simple amplifiers. Somehow, whenever I read schematics and tutorials about in-amps, I am stumped by certain terms like high-impedance, CMRR, virtual grounds. With this, I guess that I lack some foundation knowledge to begin with.
Can you suggest a learning path towards mastery of designing/using instrumentation amplifiers?
