Instrumentation Amplifier

[Jadeit]

I have in front of me a circuit in which the instrument amplifier is assembled from three amplifiers in the LM324AD,
resistors are SMD 1 or 0.1% accuracy.+12V power supply, the gain can be adjusted with a multi-turn trimmer 5k in the range of 60 to 600.
The amplifier reads the two input voltages ( over 400mV, 2V max) and amplifies the difference for the 14-bit ADC, which reads it approximately 1x per second.
Real temperature range is 0-35C , extended -10-45C

I would like to simplify the circuit, i.e. replaced by instrumentation amplifier in SO8.
A +5V power supply would be enough, the price should not differ much from the current solution and, above all, I would like the amplifier to be commonly available in the long term.
What instrument amplifier would you recommend?

 

[KlausST]

Hi,

if I had to do the job, I´d go to the internet site of my electronics distributor and use the selection guide.

Klaus

 

[danadakk]

Guides here :

https://www.analog.com/en/product-category/instrumentation-amplifiers.html

Filterable table :

https://www.analog.com/en/parametricsearch/13010#/

Regards, Dana.

 

[FvM]

Shouldn't we use an amplifier that has a chance to achieve 14 bit precision. LM324 can't.

 

[danadakk]

Precisely, reason OP is asking for IA I gather, as they are laser trimmed on production
line (most), :

https://www.analog.com/media/en/training-seminars/design-handbooks/designers-guide-instrument-amps-chIII.pdf

An example of CMR performance :

Regards, Dana.

 

[dick_freebird]

I liked AD620; whether it suits your requirements I would
have to expend personal effort, to say.

 

[Ficumard]

soccer skills world cup​

I have in front of me a circuit in which the instrument amplifier is assembled from three amplifiers in the LM324AD,
resistors are SMD 1 or 0.1% accuracy.+12V power supply, the gain can be adjusted with a multi-turn trimmer 5k in the range of 60 to 600.
The amplifier reads the two input voltages ( over 400mV, 2V max) and amplifies the difference for the 14-bit ADC, which reads it approximately 1x per second.
Real temperature range is 0-35C , extended -10-45C

I would like to simplify the circuit, i.e. replaced by instrumentation amplifier in SO8.
A +5V power supply would be enough, the price should not differ much from the current solution and, above all, I would like the amplifier to be commonly available in the long term.
What instrument amplifier would you recommend?

You can refer to INA128: low noise, rail-to-rail output, wide gain range (1 to 1000), good temperature stability. An external resistor may be required to set the gain.

 

[tracyberge]

I have in front of me a circuit in which the instrument amplifier is assembled from three amplifiers in the LM324AD,
resistors are SMD 1 or 0.1% accuracy.+12V power supply, the gain can be adjusted with a multi-turn trimmer 5k in the range of 60 to 600.
The amplifier reads the two input voltages ( over 400mV, 2V max) and amplifies the difference for the 14-bit ADC, which reads it approximately 1x per second.
Real temperature range is 0-35C , extended -10-45C

I would like to simplify the circuit, i.e. replaced by instrumentation amplifier in SO8.
A +5V power supply would be enough, the price should not differ much from the current solution and, above all, I would like the amplifier to be commonly available in the long term.
What instrument amplifier would you recommend?

An IC instrumentation amplifier typically contains closely matched laser-trimmed resistors, and therefore offers excellent common-mode rejection. Examples include INA128, AD8221, LT1167 and MAX4194.

 

[danadakk]

You can always start here :

https://www.digikey.com/en/products/filter/instrumentation-op-amps-buffer-amps/687?s=N4IgjCBcpgbB0QGMoDMCGAbAzgUwDQgD2UA2iAMwCsAHAJw2wgC6hADgC5QgDKHATgEsAdgHMQAXwmEATGRAjsAgK4BbXMI7oOgosIAE6VW0yDUg3PxYSgA

https://www.analog.com/en/product-category/instrumentation-amplifiers.html

Regards, Dana.