Instrumentation amplifier

[H161648]

I need to design a instrumentation amplifier. I read somewhere other input of instrumentation amplifier could not be zero. What could be other appropriate signal that could be applied??? please help...

 

[jan.didden]

Sorry, I do not understand your question. There are many examples of instrumentation amplifiers online.

What is your use for it?

Jan

 

[P.Lacombe]

Please be more specific. What is the exact purpose of the amp you need ? What kind of electrical signal you want to amplify ? What are you expecting at the output ? Etc.

Pierre.

 

[H161648]

I need to design a voltage amplifier. when I simulate it. In output I get dc but not ac.

 

[jan.didden]

Schematic?

 

[H161648]

Here, I have attached schematic. Have a look at it.

 

[Mooly]

There is no negative rail for the opamps. Add that and it will work.

 

[H161648]

I have tried adding that also... But not working...

 

[Mooly]

What doesn't work when you do that ?

 

[H161648]

there is no change in output doing that

 

[Mooly]

It works You have no output because both inputs are set up the same. Add a 180 degree shift to one of the voltage sources.

Try this.

 

[H161648]

ok. Thank you.
Is it possible to design in amp without dual power supply(without giving negative voltage)??

 

[Mooly]

Yes and no... its not ideal.

You would need to bias both inputs to half supply voltage and connect R4 to this half supply voltage point. The inputs and the output would then need to be AC coupled.

If you do that, use FET opamps and create a single half supply (it doesn't have to be exact) reference point.

 

[H161648]

Can you please explain? I am not getting you.

 

[H161648]

I am new at this. please help

 

[Mooly]

Something like this.

 

[H161648]

Heya, its working quite well. But as soon as I change my input to 1.2, it shows square wave in output. I s it bcoz of resistor values??

 

[Mooly]

You have to much gain in relation to the low supply voltage. Try making R6 into 20k

Have to leave it for now

 

[H161648]

Thank you.

 

[H161648]

heya, it is working quite well!!! Thanks a ton.
Whenever you get time, Can you please explain me, why did you add those capacitors and give me some document so that I can go in basics of that?
Thanks a ton in advance.