Why not "instrumentation amplifiers"

[jackinnj]

ok, I was reading one of the ADI ap-notes on instrumentation amplifiers, I realize that they aren't any good as integrators and differentiators, are somewhat expensive -- but why aren't people using them as gain blocks in audio applications? Is it just the expense, is it the necessity of nulling offset, <em> dit a mois pour

 

[Jocko Homo]

Maybe you don't use them.......

I know people who do.....especially for balanced inputs.

Jocko

 

[thylantyr]

... because most people don't listen
to instrumental music ? .......

 

[stokessd]

Lots of people DO use them. I have a phono stage design which uses BB INA103's in the front end.

They can be quite good, amazingly good, but as you stated, they aren't as universal as an op-amp.


Sheldon

 

[mikek]

Re: Why not &quot;instrumentation amplifiers&quot;

ok, I was reading one of the ADI ap-notes on instrumentation amplifiers, I realize that they aren't any good as integrators and differentiators, are somewhat expensive -- but why aren't people using them as gain blocks in audio applications? Is it just the expense, is it the necessity of nulling offset, <em> dit a mois pour

...see:

http://www.jensen-transformers.com/an/ingenaes.pdf

 

[fmak]

Lots of people DO use them. I have a phono stage design which uses BB INA103's in the front end.

-----------------------------------------------
I have one of these in a Carver Active/Passive Preamp. The balanced output is passive; the single ended has gain and contains the IN103. In comparison with the passive mode, the single ended mode doen't sound very good at all - you wouldn't use it unless you MUST.

 

[vince8]

they work...

yes,I built the design found in 'audio amateur' 6/95 ; 'An instrumentation preamp' and over the yrs. substituted various op-amps for the originally speced tl-072's. I am quite impressed with this simple design and still use it today-

 

[mikek]

Re: they work...

yes,I built the design found in 'audio amateur' 6/95 ; 'An instrumentation preamp' and over the yrs. substituted various op-amps for the originally speced tl-072's. I am quite impressed with this simple design and still use it today-

Do you have the schematic...can you post it? 🙂

 

[jackinnj]

Re: they work...

yes,I built the design found in 'audio amateur' 6/95 ; 'An instrumentation preamp' and over the yrs. substituted various op-amps for the originally speced tl-072's. I am quite impressed with this simple design and still use it today-

Are you sure the design wasn't in 2/95 "An Instrumentation Preamp" ?

While there are now better power supply designs, the author did add a soft start feature which prevented turn-on thump, and a soft-finish feature which powered off the preamp first, then the power supply. The pre-amp used multiple TL-072's in an "instrumentation" configuration, but not an off-the-shelf instrumentation operational amplifier.

I have some ADI and TI (Burr-Brown) Instrumentation ampls to play with. I guess the thing to do is compare to the TL-072's.

Jack

 

[jackinnj]

Here's a link to the Analog Devices article on Instrumentation Amplifiers: http://www.analog.com/UploadedFiles/Application_Notes/442106604AN244.pdf

 

[PGW]

Instrumentation amps are (were) generally designed for measurement applications where a very high input impedance was desirable, and so the design og these op-amps tended to focus on low voltage noise. So until relatively recently only instrumentaion amps offered the sort of noise performance required for an all op-amp preamplifier, compare with discret front end designs.

Modern op-amps with audio applications in mind generally have better balance between voltage and current noise (e.g AD797), are suitably low noise, and are probably easier to design with IMO.

 

[vince8]

instrumentation op-amp

yes,it was the 2/95 edition of audio electronics.I was looking at the month,(june) and thought 6/95 was appropriate. In any case,I'm not sophisticated enough to argue the merits of this design over another. I built it without the 'de-thumping' additions...with a decent +- 15 volt supply, and have played with the gain/ various resistors, and different ways of taking signal from source to power amp. Mikek...I have no scanner to share schematic, but it's essentially the same as has been already posted- I'm hoping I'll not be banned for playing with these op-amps...which are only for people in a hurry-?